Method for forming electrophotographic image and electrographic device

ABSTRACT

A method for forming an electrophotographic image and a device for forming an image on a transfer material by the steps for charging, exposing, developing and transferring, and recovering the toner remained untransferred in the step for cleaning by recovering, wherein the toner used in the step for developing has a total surface area ratio Z of additive, which is calculated by Z=(Ht·Wt)/(H·W), satisfies 0.5≦Z≦1.5, the electrophotographic photoconductor used comprises at least a photosensitive layer and a filler-containing protective layer provided on a conductive support in that order, and the angle of repose of the toner to the protective layer surface of the electrophotographic photoconductor is 30° or less.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for forming anelectrophotographic image and electrophotographic device and, moreparticularly, to a method for forming an electrophotographic image andelectrophotographic device using a toner having a total surface arearatio of additive in toner of 0.5-1.5 and an angle of repose of toner tothe protective layer of a electrophotographic photoconductor of 30° orless.

[0003] 2. Description of the Related Art

[0004] Conventionally, there are various electrophotographic methodsknown, which generally relates to a method of forming an electrostaticlatent image on an image carrier (photoconductor) by various meansutilizing a photoconductive material, developing the latent image withtoner to form a visible image, transferring the toner image to atransfer material such as paper if necessary, and fixing the toner imageon the transfer material by applying heat, pressure or the like tocreate a printed article.

[0005] For known methods for visualizing the electrical latent image,cascade development method, magnetic brush development method, pressuredevelopment method and the like may be mentioned. Further, there is alsoknown a method in which magnetic toner released by a rotating sleevehaving magnetic pole in the center is fed into an electric field createdin between a photoconductor and a sleeve.

[0006] A one-component developing method allows reduction in size andweight of a developing device itself because it does not require carrierparticles such as glass bead, iron powder, or the like as required in atwo-component method. In order to maintain the toner concentration in acarrier constant, the two-component development method requires a devicefor detecting the toner concentration and supplying necessary amount ofthe toner, hence the development device is increased both in size andweight. On the other hand, one-component developing method is preferablein terms of reduction in the size and weight of the developing devicebecause a device for detecting is not necessary.

[0007] For printer devices, LED and LBP printers are becoming mainstreamtechnology in the market accompanying a technical trend to attain higherresolution, namely 400, 600 dpi in the past to 800, 1200 dpi at present.Concurrent with this trend, demand for higher definition in thedevelopment method is also pursued. Further, in the field of copyingmachines, digitalization prevails to cope with demand for improvedfunctionality. Since the digitalization primarily intends formation ofan electrostatic image with laser, aiming at higher resolution isbecoming the focus of advancement of the technical trend. Accordingly,the developing method also calls for higher resolution/higher definitionin the field of copying machines similarly to printers. Therefore,particle diameter of a toner is increasingly becoming smaller, and forinstance, toners having small particle diameter existing in specificparticle diameter distributions are proposed in Japanese PatentApplication Laid-Open Nos. 3-181952, 4-162048, and the like.

[0008] The toner image formed on a photoconductor during developingprocess is transferred to a transfer material in the transfer process,and the residual toner untransferred on the photoconductor is cleaned inthe cleaning process and stored in a waste toner vessel. In the cleaningprocess, generally, blade cleaning, fur brush cleaning, roller cleaningand the like are used. From the viewpoint of device configuration, suchcleaning device is an inevitable equipment, and thus leads to anenlargement of the device as a whole, causing difficulty in realizing adevice compact in size. Further, from the viewpoint of environmentalprotection, a system which minimizes the toner waste and promotingeffective use of toner is desired, along with toner having high transferability.

[0009] According to the reduction in the size (or diameter) of tonerparticle, the adhesive force of the toner particle to a latent imagecarrier (mirror image force, van der Waals force, etc.) tends toincrease, compared to the Coulomb's force applied to the toner particleat the time of transfer, consequently causing amount of the tonersuntransferred to increase.

[0010] In a roller charging method, the physical and chemical effect ofthe electrostatic latent image carrier surface by a discharge generatedbetween an charge roller and the electrostatic latent image carrier ishigh, compared with that in a corona electric charging method, and awear caused by the deterioration of the surface of photoconductor tendsto occur, particularly, when an organic photoconductor/blade cleaningare used in combination, thus leaving a problem of shortened life (thecombination of direct charging/organic photoconductor/one-componentmagnetic development method/contact transfer/blade cleaning is themainstream technology in copying machines, printers, facsimiles and thelike in the field demanding low price, small size and light weight,because reduction in cost, size and weight of an image forming device isrelatively easy).

[0011] A study on adding filler to the protective layer of theelectrophotographic photoconductor was carried out in an attempt toprevent the wear of the electrophotographic photoconductor (improvementin printing resistance). A study on protective layer used as surfacelayer of the photoconductor initially directed on organicphotoconductors, including, for example, those disclosed in JapanesePatent Publication Nos. 2-3171, 2-7058, 3-43618, and the like. When theprotective layer is provided on the surface of an inorganicphotoconductor, fillers having relatively low resistance were suitablyused as the protective layer (Japanese Patent Application Laid-Open Nos.63-254462 and 63-254463). Therefore, electricity was charged more oftenin the protective layer as a whole or in the interface of protectivelayer/inorganic photosensitive layer rather than on the surface of theelectrophotographic photoconductor. When the latent image was formed noton the surface of electrophotographic photoconductor but on the innerportion of the protective layer (including the interface with theinorganic photosensitive layer), an advantage was confirmed in that theinfluence of the shapes (flaw, etc.) which appear on the surface of theelectrophotographic photoconductor was minimized. However, in order torender the surface layer to act as the protective layer, it is necessaryto add a large amount of a conductive metal oxide as the filler to beadded to the surface layer. In this case, even if the transparency ofthe surface layer is ensured by choosing an appropriate material, thebulk or surface resistance of the surface layer deteriorates, oftencausing image blurring in repeated use. To solve such disadvantages,Japanese Patent Publication No. 2-7057 and Patent No. 2675035 disclosesa method to change the conductive metal oxide concentration in thesurface layer in the depth direction of the coating surface, whereby theimage blurring and flowing are suppressed.

[0012] In order to suppress image blurring, a method for mounting a drumheater to heat the electrophotographic photoconductor during the processis disclosed. However, in order to mount the drum heater to preventimage blurring by heating the electrophotographic photoconductor, theelectrophotographic photoconductor needs to have large diameter, andtherefore such method could not be applied to electrophotographicphotoconductors having small diameters which are the focus of mainstreamtechnology accompanying miniaturization of electrophotographic devices.Moreover, it is difficult to improve durability of theelectrophotographic photoconductors having minor diameters. Further, thesize of the device is inevitably increased by mounting the drum heater,thus causing increase in electric power consumption, and time consumingstart up and the like, leaving various problems unsolved.

[0013] On the other hand, a surface layer (protective layer) using afiller having low resistance was laminated on a electrophotographicphotoconductor using an organic charge generating material and chargetransporting material (referred to as OPC) using the techniqueabove-mentioned, and tested in repeated uses. As a result, image flowingwas observed assumedly due to the poor matching property with OPC.Substantially the same result was observed in a method creating aconcentration distribution in the surface layer of the conductive metaloxide, the method which was effective for inorganic photoconductors. Thereason for the cause of image flow is not clear. In the recentelectrophotographic process using organic photoconductors, a digitalsignal is used in a manner to be dotted-in when writing on thephotoconductor, the manner which is very different from the mannerapplied for inorganic photoconductors. From the viewpoint of machineconfiguration, the level of resolution required has changeddramatically, thus rendering such phenomenon (defects) obvious.

[0014] Under such circumstances, it is essential to use a non-conductiveand highly resistant filler in the surface layer of the organicphotoconductor. However, use of highly resistant filler often causes aproblem of increased residual potential. The frequently observedincrease in residual potential leads to a high bright part potentialwithin the electrophotographic device, causing reduction in imagedensity or tones. Although it is necessary to raise the dark partpotential for compensation, the increase in dark part potential bringsup the field intensity, which not only causes an image defect such astoner deposition on the background of images, and the like but alsoleads to reduced life of the photoconductor. From such a viewpoint, acombination of two kinds of fillers was examined, but the problem inwhich the presence of a large amount of low resistant filler on thesurface of photoconductor causes image blur in repeated use cannot beprevented, thus leaving a basic problem unsolved.

[0015] To suppress presence of residual potential in the related art,use of photoconductive layer as the protective layer is disclosed(Japanese Patent Publication Nos. 44-834, 43-16198, and 49-10258).However, since the amount of light reaching the photosensitive layer isreduced due to absorption of light by the protective layer, the problemof deterioration in sensitivity of the photoconductor arises, whileexhibiting less effect.

[0016] It is also disclosed to make the protective layer substantiallytransparent to suppress accumulation of residual potential bydetermining average particle diameter of a metal or metal oxidecontained in the filler to be 0.3 μm or less (Japanese PatentApplication Laid-Open No. 57-30846). In this method, an effect ofsuppressing an increase in residual potential was confirmed, it is notsufficient to provide basic solution to the problem. An increase inresidual potential when filler is contained may possibly be caused bythe charge trap or the dispersibility of the filler due to presence ofthe filler, rather than by the charge generating efficiency. Thetransparency may be ensured by improving the dispersibility even whenthe average particle diameter of the filler is 0.3 μm or more, whiletransparency of the film is sacrificed when the filler is rathercoagulated even when an average particle diameter is 0.3 μm or less.

[0017] Other means for suppressing the rise in residual potentialinclude: addition of Lewis acid or the like in the protective layer(Japanese Patent Application Laid-Open No. 53-133444); addition oforganic protonic acid in the protective layer (Japanese PatentApplication Laid-Open No. 55-157748); addition of electron receivingmaterial (Japanese Patent Application Laid-Open No. 2-4275); andaddition of wax having acid value of 5 (mgKOH/g) or less (JapanesePatent Application Laid-Open No. 2000-66434). These methods conceivablyare based on observation that charge easily reaches the surface whencharge injecting property is improved at the interface of protectivelayer/charge transporting layer and forming of a low resistant portionin the protective layer. Although the effect of reducing the residualpotential is confirmed in these methods, they have a side effect such asimage blurring and the like to clearly show in the image. Further,addition of an organic acid tends to cause deterioration indispersibility of the filler, and its effect is insufficient to solvethe problem.

[0018] To realize a higher image quality in an electrophotographicphotoconductor containing filler to improve durability, it is importantnot only to suppress the image blurring or rise in residual potential,but also for the charge to linearly reach the surface of thephotoconductor without being disturbed by the filler in the protectivelayer. The dispersibility of the filler in the protective layer film hasa great influence on the wear resistance. When the charge injected tothe protective layer from the charge transporting layer moves to thesurface of the protective layer, the move of the charge may be disturbedby the filler coagulated, thus the dot formed by the toner is dispersed,and consequently deteriorates resolution. When the protective layer isprovided, the light transmitting property tends to deteriorate due toscattering of the recording light by the filler. Such phenomenon alsohas a serious adverse effect on the resolution. The influence on thelight transmitting property is also closely related to thedispersibility of the filler. The dispersibility of the filler also hasa great influence on the wear resistance. The filler when highlycoagulated will affect wear resistance due to poor dispersibility.Accordingly, to achieve high image quality simultaneously with highdurability in an electrophotographic photoconductor having a protectivelayer containing the filler for improvement of durability, it isimportant not only to suppress the image blurring or rise in residualpotential, but also to improve dispersibility of the filler in theprotective layer film.

[0019] Effective means for solving both of the problems at the same timehave not been presented as of today. When the filler is contained in theprotective layer of the electrophotographic photoconductor to improvedurability, the influence of image blurring or rise in residualpotential is caused, leaving the problem of image quality improvementunsolved. Further, improvement in durability of a electrophotographicphotoconductor having small diameter which requires highest durabilityfrom the standpoint of loading the drum heater in order to reduce suchinfluence has not been realized, thus making downsizing of the device,and reduction of power consumption, difficult.

[0020] Organic photoconductors which has been surpassing inorganicphotoconductors in terms of photosensitivity, spectral sensitivityrange, non-pollution property, electrostatic durability and the like,the improvement in mechanical durability is a pressing need to fullyutilize their advantages, and the development of such organicphotoconductors having improved mechanical strength has been desired foruse in highly durable machines and process designs.

[0021] When the life of the photoconductor is free from image scrapingas the result of improvement in wear resistance of the photoconductor,the life of the photoconductor depends on the electrostatic life of theelectrophotographic photoconductor. Concretely, the reduction inelectrostatic property of the electrophotographic photoconductor(particularly, local potential leak) causes a defect appearing as spots(toner deposition on the background of images, black spot, etc.) in asurface portion (white) which is not present on a document to be copied.Such defect is often mistaken as a dot in a drawing or a period, commaor the like in an English document, and may be a fatal defect of image.

[0022] As described above, the toner and photoconductor used for animage forming method aiming at high transfer ability are required tohave excellent releasability. In Japanese Patent Application Laid-OpenNo. 11-272003 or the like, an electrophotographic photoconductorcharacterized by having a large contact angle of the outermost layersurface of the electrophotographic photoconductor with pure water isproposed. However, even if the contact angle of the outermost layersurface of the electrophotographic photoconductor with pure water isincreased, there is no correlation of releasability of the toner to theelectrophotographic photoconductor in actual situations, further, suchelectrophotographic photoconductor has insufficient transfer ability andcleanability and requires a further improvement.

SUMMARY OF THE INVENTION

[0023] The present invention has an object to provide a method forforming an electrophotographic image and electrophotographic deviceusing the toner and electrophotographic photoconductor in which theproblems of the related art are solved.

[0024] Namely, the present invention has an object to provide a methodfor forming an electrophotographic image and electrophotographic deviceusing a toner excellent in transfer property to minimize generation ofthe toner remained untransferred and never causes filming onto acleaning member or on the photoconductor or capable of suppressing thesephenomena, and to provide a method for forming an electrophotographicimage and electrophotographic device using a photoconductor havinglong-life, excellent in releasability and slidability to minimizescraping even after long-term use and repeated printing.

[0025] As a result of the earnest studies to achieve above mentionedobjects, focusing to releasability of the photoconductor to the toner,the present inventors attained the present invention.

[0026] According to the present invention, method for formingelectrophotographic image as described in the following 1-10 andelectrophotographic device described in 11-25 are provided.

[0027] In a method for forming electrophotographic image and anelectrophotographic device of the present invention, a toner having atotal surface area ratio X of additive of 0.5-1.5 and a photoconductorcomprising a filler-containing protective layer on a photosensitivelayer are used, and the angle of repose of the toner to the protectivelayer surface of the photoconductor is set to 30° or less, whereby thefilming on the cleaning member and the filing on the photoconductor arenever caused, and the scraping of photoconductor is remarkably reduced.

[0028] The toner to be used preferably has a roundness of 0.95 or more.The filler contained in the protective layer of the photoconductorpreferably comprises an inorganic pigment or metal oxide having aspecific resistance of 1×10¹⁰ Ω·cm or more.

[0029] The protective layer preferably contains a charge transportingmaterial, and the charge transporting material preferably comprises apolymer having electron-donating group. The protective layer alsopreferably contains an organic compound having acid value of 10-400(mgKOH/g). An excessive amount of silicone oil is preferably added tothe outermost layer of the photoconductor, and the charge generatingmaterial contained in the photoconductor preferably comprises a titanylphthalocyanine specified above or an azo pigment represented by thegeneral formula (A). Further, the conductive support surface of thephotoconductor is preferably anodized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a typical cross-sectional view showing a structuralexample of an electrophotographic photoconductor of the presentinvention.

[0031]FIG. 2 is a typical cross-sectional view showing anotherstructural example of the electrophotographic photoconductor of thepresent invention.

[0032]FIG. 3 is a typical cross-sectional view showing the otherstructural example of the electrophotographic photoconductor of thepresent invention.

[0033]FIG. 4 is a schematic view for describing an electrophotographicdevice according to the present invention.

[0034]FIG. 5 is a schematic view showing a non-contact chargingmechanism (comprising a gap retaining mechanism formed on an chargingmember side).

[0035]FIG. 6 is a schematic view showing another electrophotographicdevice according to the present invention.

[0036]FIG. 7 is a flow chart showing an angle-of-repose measuring workin Examples of the present invention.

[0037]FIG. 8 is an XD spectral view of titanyl phthalocyanine containedin the charge generating layer of a photoconductor of Example 9 of thepresent invention.

DESCRIPTION OF THE PREFERED EMBODIMENTS

[0038] The present invention is further described in detail.

[0039] An electrostatic latent image developer toner of the presentinvention at least comprises a toner particle and at least one additive,and the toner particle contains a binder resin and a coloring agent.

[0040] (Toner Particle and Additive)

[0041] The toner of the present invention is required to have a totalsurface area ratio Z of additive in the toner, calculated byZ=(Ht·Wt)/(H·W), satisfying 0.5≦Z≦1.5, and having an angle of repose ofthe toner to the filler-containing outermost layer surface of aphotoconductor used for an electrophotographic imaging method forrecovering the residual toner in the step for cleaning.

[0042] The above reference marks represent the following numericalvalues.

[0043] H: Specific surface area of toner particles (m²/g)

[0044] W: Weight content of toner particles (%)

[0045] Ht: Specific area of additives (m²/g)

[0046] Wt: Content ratio of additives (%)

[0047] The specific surface area mentioned herein means a specificsurface area measured using a specific surface area measuring instrument[MONOSORB MS-12 made by YUASA IONICS] according to BET method.

[0048] When the total surface area ratio Z is Z<0.5, it is difficultthat the angle of repose of the toner to the protective layer surface ofthe photoconductor satisfies 30° or less, and the use of such a toner inthe one-component developing method causes a toner supply failure byinsufficient toner fluidity. When the total surface area ratio Z is1.5<Z, the angle of repose of the toner to the protective surface layerof the photoconductor substantially satisfies less than 30°, but thefilming to cleaning member and thin layer regulating member occurs.Further, the filming to photoconductor occurs, too, and the scraping ofphotoconductor is deteriorated after long-term and many-sheet printingto remarkably shorten the life of the photoconductor.

[0049] When the angle of repose of the toner to the protective layersurface of the photoconductor exceeds 30°, the deterioration in thetoner and the photoconductor are caused.

[0050] The fluidity (the angle of repose of toner) referred to in thepresent invention is determined as follows. A sample (100 g) on a sieveis fallen by gravity with vibration and filled in a cylindrical vessel 5cm in height and 5 cm in diameter, then the toner which exceeds thesurface of the cylindrical vessel is removed, and a flat aluminum plateformed by coating the protective layer surface of the photoconductor isplaces on the cylindrical vessel filled with toner. The cylindricalvessel is turned upside down while being closely fitted to the coatedflat aluminum plate, and gently pulled up. The angle of repose of theaccumulated sample of toner formed at this time is determined.

[0051] As the additives of the toner in the present invention, knownadditives such as inorganic fine particle, organic fine particles andthe like may be used. Among them, inorganic fine particles such assilica, titania, alumina, cerium oxide, strontium titanate, calciumcarbonate, magnesium carbonate, calcium phosphate, etc., and organicfine particles such as fluorine-containing resin fine particle,silica-containing resin fine particle, nitrogen-containing resin fineparticle, etc. are preferably used. The additive surface may besubjected to surface treatment according to purposes. The surfacetreatment agents include silane compounds, silane coupling agents, andsilicone oil for performing hydrophobic treatment, and the like.

[0052] Further, it is preferable to include at least two additivesdiffered in particle diameter from the point of preventing thedeterioration of toner fluidity caused by the burying of the additive tothe toner parent body with a lapse of time to prevent the resultingimage unevenness, and from the point of enhancing the adhesive force tothe toner to prevent the separation of the additives from the tonerwhich causes a sensitive material flaw and an image omission. Suchadditives preferably have a particle diameter difference of about 2-5times in average particle diameter. When at least two additives differedin particle diameter are included, the additive with major particlediameter plays a role of a spacer to prevent the additive with minorparticle diameter effective for toner fluidity from being buried in thetoner parent body, and the toner fluidity can be kept.

[0053] The additive with large particle diameter means a one having aBET specific surface area of 20-80 m²/g. Various surface-treated onesmay be used when their BET specific surface areas are within this range,and a one with 20-50 m²/g is more preferable. When the BET specificsurface area is less than 20 m²/g, the image unevenness resulted fromthe deterioration in toner fluidity is apt to occur, and it is difficultto improve the adhesive force to the toner, and the separation from thetoner easily occurs, causing the sensitive material flaw and imageomission. The additive with small particle diameter means a one having aBET specific surface area of 100-250 m²/g, and various surface-treatedones may be used when their BET specific surface areas are within thisrange. A one with 120-200 m²/g is more preferable because it iseffective, particularly, for reducing the adhesive force of the toner.

[0054] (Parent Toner Particle)

[0055] The parent toner particle of the present invention preferably hasa roundness of 0.95 or more. A toner produced by an air pulverizationmethod, which is conventionally mainly used, has a highly irregularshape. The lightly fused toner in the early stage is scraped off fromthe photoconductor body by the abrasive force resulted from theirregularities, so that the fusion is relatively less developed to aserious level. The toner of the present invention has a rounded shape,compared with the toner produced by the conventional air pulverizationmethod, and it is assumed that the fusion is hardly caused under a severcondition because the abrasive property of the toner particle itself isreduced. As the reason, the frictional resistance of the toner with thephotoconductor is conceivably reduced to reduce the frictional heatgenerated, so that the fusion is not developed.

[0056] The measurement of roundness in the present invention isperformed using a flow type particle image analyzer (FPIA-1000) made byTOA DENSHI.

[0057] The preparation of a parent toner particle having a roundness of0.95 or more can be prepared by an emulsion polymerization coagulationmethod of polymerizing a polymeric monomer of a binder resin by emulsionpolymerization and mixing the resulting dispersion with a coloring agentand, as necessary, a dispersion of release agent, static controllingagent, offset preventing agent, and the like followed by coagulation andfusing to obtain the toner particle; a suspension polymerization methodof suspending a polymeric monomer for obtaining the binder resin, acoloring agent and, as necessary, a solution of release agent, staticcontrolling agent, offset preventing agent, and the like to an aqueoussolvent followed by polymerization; a solution suspension method ofsuspending a binder resin, a coloring agent and, as necessary, asolution of release agent, static controlling agent, offset preventingagent, and the like to an aqueous solvent followed by pelletization; andthe like. A kneading pulverization method of kneading a binder resinwith a coloring agent and, as necessary, a release agent, a staticcontrolling agent, an offset preventing agent, and the like followed bypulverization and classification is also adaptable. Further, in thepreparation, a thermal energy may be imparted to an amorphous tonerparticle obtained by the gas pulverization to change the shape, or aflock may be further adhered to the toner particle obtained by the abovemethod as a core followed by fusing to impart a core shell structure.

[0058] The binder resins used for the preparation of the toner particlein the present invention include single polymers or copolymers ofstyrenes such as styrene and chlorostyrene; monoolefins such asethylene, propylene, butylenes, and isoprene; vinyl esters such as vinylacetate, vinyl propionate, vinyl benzoate, and vinyl lactate;α-methylene aliphatic monocarboxylates such as methyl acrylate, ethylacrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenylacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate,and dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinylethyl ether and vinyl butyl ether; vinyl ketones such as vinyl methylketone, vinyl hexyl ketone and vinyl isopropenyl ketone; and the like.Particularly, typical binder resins include polystyrene, styrene-acrylicalkyl copolymer, styrene-methacrylic alkyl copolymer,styrene-acrylonitrile copolymer, styrene-butadiene copolymer,styrene-maleic anhydride copolymer, polyethylene, polypropylene, and thelike. Further, polyester, polyurethane, epoxy resin, silicone resin,polyamide, modified rosin, paraffin wax and the like are also usable.

[0059] The typical coloring agents used for the preparation of the tonerparticle in the present invention include dyes and pigments such ascarbon black, aniline blue, chalcoyl blue, chromium yellow, ultra marineblue, de Pont oil red, quinoline yellow, methylene blue chloride,phthalocyanine blue, malachite green oxalate, lamp black, rose Bengal,C.I. pigment·red 48: 1, C.I. pigment·red 122, C.I. pigment·red 57:1,C.I. pigment·yellow 97, C.I. pigment·yellow 17, C.I. pigment·blue 15:1,C.I. pigment·blue 15:3, and the like.

[0060] To the toner particle of the present invention, a release agentfor preventing offset may be added as necessary in addition to thebinder resin and the coloring agent. Such release agents include waxessuch as low molecular polypropylene, low molecular polyethylene, and thelike. As the static controlling agent, known ones may be used. Amongthem, an azo-based metal complex compound or a metal complex compound ofsalicylic acid can be suitably used.

[0061] The toner particle of the invention preferably has an averageparticle diameter of 5-11 μm similarly to general toner particles, andthe range of 4-8 μm is more preferable. When the average particlediameter exceeds 11 μm, the toner particle is not faithfully developedto latent images of dot and line, often deteriorating the reproductionof a photographic image or the reproduction of a fine line. When theaverage particle diameter is less than 3 μm, the surface area per tonerunit is increased to make the control of electrostatic property andtoner fluidity, and a stable image cannot be often obtained.

[0062] The average particle diameter and particle diameter distributionof the toner in the present invention are determined using a Coultercounter TA-II or Coulter multiple sizer (made by COULTER) or the like.

[0063] An electrophotographic photoconductor of the present invention isfurther described with reference to the drawings.

[0064]FIG. 1 is a typical cross-sectional view showing a structuralexample of the electrophotographic photoconductor of the presentinvention, wherein a single layer photosensitive layer 33 mainlycomprised of a charge generating material and a charge transportingmaterial is provided on a conductive support 31, and a protective layer39 is provided on the photosensitive layer.

[0065]FIG. 2 is a typical cross-sectional view showing anotherstructural example of the electrophotographic photoconductor of thepresent invention, wherein the photosensitive layer has a laminatedstructure of a charge generating layer 35 mainly comprised of a chargegenerating material and a charge transporting layer 37 mainly comprisedof a charge transporting material, and a protective layer 39 is providedon the charge transporting layer 37.

[0066]FIG. 3 is a typical cross-sectional view showing the otherstructural example of the electrophotographic photoconductor of thepresent invention, wherein the photosensitive layer has a laminatedstructure of the charge transporting layer 37 mainly comprised of acharge transporting material and the charge generating layer 35 mainlycomprised of a charge generating material, and the protective layer 39is provided on the charge generating layer 35.

[0067] As the conductive support 31, a film-like or cylindrical plasticor paper covered with a material showing conductivity of volumeresistance 10¹⁰ Ω·cm or less, for example, a metal such as aluminum,nickel, chromium, nichrome, copper, gold, silver, platinum, etc. or ametal oxide such as tin oxide, indium oxide, etc. by evaporation orsputtering, a plate such as aluminum, aluminum alloy, nickel, stainlessor the like, or a pipe obtained by forming the plate into a crude pipefollowed by surface treatment such as cutting, super finishing,polishing or the like may be used. An endless nickel belt and endlessstainless belt disclosed in Japanese Patent Application Laid-Open No.52-36016 are also usable as the conductive support 31.

[0068] Among them, a cylindrical support consisting of aluminum, whichis easy to anodize, can be used most preferably. The aluminum referredherein includes both pure aluminum series and aluminum alloys.Concretely, aluminums or aluminum alloys of JIS 1000, 3000 and 6000series are most suitable. The anodic oxide films are obtained byanodizing various metals and various alloys in an electrolytic solution.Among them, particularly, a film called alumite obtained by anodizingaluminum or an aluminum alloy in an electrolytic solution is mostsuitable for the photoconductor of the present invention. This isparticularly excellent in the point of preventing a spot defect (blackspot, toner deposition on the background of images) generated in the usefor reverse development (negative and positive developments).

[0069] The anodic treatment is performed in an acidic bath of chromicacid, sulfuric acid, silicic acid, phosphoric acid, boric acid, sulfamicacid or the like. Among them, the sulfuric acid bath is most suitablefor the treatment. The treatment is performed, for example, within theranges of sulfuric acid: 10-20%, bath temperature:5-25° C., currentdensity: 1-4 A/dm², electrolytic voltage: 5-30 V, and treatment time:about 5-60 min, but is not limited. Since the thus-prepared anodic oxidefilm is porous and has high insulating property, the surface thereof isin an extremely unstable state. Therefore, the physical values of theanodic oxide film are apt to change by the change with time after thepreparation. To avoid it, the anodic oxide film is desirably furthersealed. The sealing treatment can be performed by dipping the anodicoxide film in an aqueous solution containing nickel fluoride or nickelacetate, by dipping the anodic oxide film in boiling water; treating thefilm with pressurized steam, or the like. Among these methods, thedipping in the aqueous solution containing nickel acetate is motepreferable. The washing treatment of the anodic oxide film is performedsuccessively to the sealing treatment. This is performed mainly for thepurpose of removing the excess of a metal salt adhered by the sealingtreatment. When the metal salt is excessively left on the surface of thesupport (anodic oxide film), it does not affect the quality of a coatingformed thereon but reversely causes a toner deposition on the backgroundof images because the low resistance component is generally left. Thewashing is generally in multiple stages although one washing with purewater is sufficient. The final washing solution is preferably as cleanas possible (deionized). In one process of the multistage washingprocesses, a physical rubbing washing with a contact member is desirablyperformed. The thickness of the thus-formed anodic oxide film isdesirably is in the range of 5-15 μm. When it is smaller than thisrange, the effect of barrier property as anodic oxide film isinsufficient, and when it exceeds this range, the time constant aselectrode is too large, often generating a residual potential ordeteriorating the responsiveness of the photoconductor.

[0070] Further, in the present invention, a conductive support 31 formedby coating a support with a conductive powder dispersed in anappropriate binder resin may also be used. Such conductive powdersinclude carbon black, acetylene black, metal powder of aluminum, nickel,iron, nichrome, copper, zinc, silver, etc., and a metal oxide powdersuch as conductive tin oxide, ITO, etc. The binder resins used togetherinclude thermoplastic and thermosetting resins or photo-curing resinssuch as polystyrene, styrene-acrylonitrile copolymer, styrene-butadienecopolymer, styrene-maleic anhydride copolymer, polyester, polyvinylchloride, polyvinyl chloride-vinyl acetate copolymer, polyvinyl acetate,polyvinylidene chloride, polyacrylate resin, phenoxy resin,polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinylbutyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole,acrylic resin, silicone resin, epoxy resin, melamine resin, urethaneresin, phenolic resin, alkyd resin and the like. Such a conductive layercan be provided by dispersing the conductive powder and the binder resinin an appropriate solvent, e.g., tetrahydrofurane, dichloromethane,methyl ethyl ketone, toluene, or the like and applied.

[0071] Further, a support comprising a conductive layer on a appropriatecylinder using a thermally shrinkable tube containing the conductivepowder in a material such as polyvinyl chloride, polypropylene,polyester, polystyrene, polyvinylidene chloride, polyethylene, rubberchloride, polytetrafluoro-ethylene or the like may also be used as theconductive support 31 of the present invention.

[0072] The photosensitive layer will be described hereinafter. Thephotosensitive layer may be formed of a single layer or a laminatedstructure, and those formed of charge generating layer 35 and the chargetransporting layer 37 will be described first.

[0073] The charge generating layer 35 is mainly comprised of a chargegenerating material, and a binder resin is often used as necessary. Asthe charge generating material, inorganic materials and organicmaterials may be used.

[0074] The inorganic materials include crystal selenium, amorphousselenium, selenium-tellurium, selenium-tellurium-halogen,selenium-arsenic compound, amorphous silicon, and the like. For theamorphous silicon, the one having a dangling bond terminated withhydrogen atom or halogen atom, or the one doped with boron atom,phosphor atom or the like may suitably be used.

[0075] As the organic materials, known materials for example, aphthalocyanine-based pigment such as metal phthalocyanine, organicphthalocyanine, etc., an azurenium salt pigment; a squaric acid methanepigment, an azo pigments having carbazole frame, an azo pigment havingtriphenyl amine frame, an azo pigment having diphenylamine frame, an azopigment having benzothiophene frame, an azo pigment having fluorenonframe, an azo pigment having distyryl oxadiazole frame, an azo pigmenthaving distyryl carbazole frame, a perylene-based pigment, ananthraquinone-based or polycyclic quinone-based pigment, a quinoneimine-based pigment, diphenylmethane and triphenylmethane-basedpigments, benzoquinone and naphthoquinone-based pigments, cyanine andazomethine-based pigments, an indigoide-based pigment, abisbenzimidazo10based pigment, and the like may be used. Such chargegenerating materials can be used independently or in combination of twoor more.

[0076] Among them, the azo pigment and/or phthalocyanine pigment areeffectively used. Particularly, an azo pigment represented by thefollowing general formula (A) and a titanyl phthalocyanine(particularly, having a maximum diffraction peak at least at 27.2° asthe diffraction peak (±0.2°) of Bragg angle 2θ to characteristic X-rays(wavelength 1.542 Å) of CuKα) may suitably be used.

[0077] [in the formula (A), Cp₁ and Cp₂, which may be the same ordifferent, each representing a coupler residual group; R₂₀₁ and R₂₀₂,which may be the same or different, each represents any one of hydrogenatom, a halogen atom, an alkyl group, an alkoxyl group and a cyanogroup, and Cp₁ and Cp₂ are groups represented by the following generalformula (B):

[0078] (in the formula (B), R₂₀₃ represents hydrogen atom, an alkylgroup such as methyl group, ethyl group, etc., or an aryl group such asphenyl group, etc.; R₂₀₄, R₂₀₅, R₂₀₆, R₂₀₇, and R₂₀₈ each representhydrogen atom, nitro group, cyano group, a halogen atom such asfluorine, chlorine, bromine, iodine, etc., an alkyl group such astrifluoromethyl group, methyl group, ethyl group, etc., an alkoxyl groupsuch as methoxy group, ethoxy group, etc., a dialkylamino group, orhydroxyl group; and X represents an atom group necessary forconstituting a substituted or non-substituted aromatic carbocyclicresidue or a substituted or non-substituted aromatic heterocyclicresidue.)]

[0079] Particularly, an asymmetric azo pigment having a structure inwhich Cp₁ is differed from Cp₂ generally satisfies photosensitivity morethan a symmetric azo pigment having a structure in which Cp₁ is the sameas Cp₂, conformable to the reduction in diameter of the photoconductorand the speeding up of the process.

[0080] Among the titanyl phthalocyanines having maximum diffractionpeaks at least at 27.2° as the diffraction peak (±0.2°) of Bragg 2θ, atitanyl phthalocyanine further having essential peaks at 9.4°, 9.6°, and24.0° and having a peak at 7.3° as the lowest angle-side peak withouthaving any peak in the range of 7.4-9.4° or having a peak at 26.3°(described in Japanese Patent Application Laid-Open No. 2001-19871) isparticularly effective for use.

[0081] These charge generating materials may be used independently or incombination of two or more.

[0082] The binder resin used for the charge generating layer 35 asnecessary includes polyamide, polyurethane, epoxy resin, polyketone,polycarbonate, silicone resin, arylic resin, polyvinyl butyral,polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone,poly-N-vinyl carbazole, polyacrylamide, polyvinyl benzale, polyester,phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinylacetate, polyphenylene oxide, polyamide, polyvinyl pyridine, celluloseresin, casein, polyvinyl alcohol, polyvinyl pyrolidone, and the like.The amount of the binder resin against 100 parts by weight of the chargegenerating material is suitably determined at 0-500 parts by weight, andpreferably 10-300 parts by weight.

[0083] The method for forming the charge generating layer 35 can begenerally divided into a vacuum thin film forming method and a castingmethod of the materials dispersed in solution.

[0084] For the former method, vacuum evaporation, glow-dischargedecomposition, ion plating, sputtering, reactive sputtering, CVD and thelike are used, and the above-mentioned inorganic materials and organicmaterials may suitably be used for the formation of the chargegenerating layer 35.

[0085] The charge generating layer by the latter casting method can beformed by dispersing the above-mentioned charge generating inorganic ororganic material with a binder resin as necessary using a solvent suchas tetrahydrofurane, cyclohexane, dichloroethane, butanone, etc. by aball mill, an attoritor, a sand mill or the like, and properly dilutingand applying the resulting dispersant. For coating application, dipcoating, spray coating, bead coating, nozzle coating, spinner coating,ring coating or the like may be used.

[0086] The appropriate thickness of the charge generating layer 35 isabout 0.01-5 μm, preferably 0.1-2 μm.

[0087] The charge transporting layer 37 can be formed by dissolving ordispersing the charge transporting material and the binder resin in anappropriate solvent, and applying the resulting solution after drying.As necessary, a plasticizer, a leveling agent, an antioxidant and thelike may be added thereto.

[0088] The charge transporting materials include hole transportmaterials and electron transport materials. The electron transportmaterials include electron accepting materials such as chloroanil,bromoanil, tetracyanoethylene, tetracyanoquinodimethane,2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone,2,6,8-trinitro-4H-indeno[1,2,-b]thiophene-4-on,1,3,7-trinitrodibenzothiophene-5,5-dioxide, benzoquinone derivative, andthe like.

[0089] The hole transport materials include poly-N-vinyl carbazole andderivatives thereof, poly-γ-carbazolylethyl glutamate and derivativesthereof, pyrene-formaldehyde condensate and derivatives thereof,polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives,oxadiazole derivatives, imidazole derivatives, monoarylaminederivatives, diarylamine derivatives, triarylamine derivatives, stilbenederivatives, α-phenyl stilbene, benzidine derivatives, diaryl methanederivatives, triaryl methane derivatives, 9-styrylanthracenederivatives, pyrazoline derivatives, divinyl benzene derivatives,hydrazone derivatives, indene derivatives, butadiene derivatives, pyrenederivatives, bisstilbene derivatives, enamine derivative, etc., andother known materials. These charge transporting materials may be usedindependently or in combination of two or more.

[0090] The binder resins include thermoplastic and thermosetting resinssuch as polystyrene, styrene-acrylonitrile copolymer, styrene-butadienecopolymer, styrene-maleic anhydride copolymer, polyester, polyvinylchloride, polyvinyl chloride-vinyl acetate copolymer, polyvinyl acetate,polyvinlydene chloride, polyarate, phenoxy resin, polycarbonate,cellulose acetate resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxyresin, melamine resin, urethane resin, phenolic resin, alkyd resin andthe like.

[0091] The amount of the charge transporting material is properlydetermined at 20-300 parts by weight, preferably 40-150 parts by weightto 100 parts by weight of the binder resin. The thickness of the chargetransporting layer is preferably determined in the range of about 5-100μm. The solvents used herein include tetrahydrofurane, dioxane, toluene,dichloromethane, monochlorobenzene, dichloroethane, cyclohexane, methylethyl ketone, acetone and the like.

[0092] A polymer having electron-donating group may be contained in thecharge transporting layer. The polymers having electron-donating groupinclude a high molecular charge transporting material having thefunction of charge transporting material and the function of binderresin, or a polymer laid in a monomer or oligomer state havingelectron-donating group at the time of film forming the chargetransporting layer and finally having a two-dimensional orthree-dimensional cross-linked structure by being hardened orcross-linked after film forming.

[0093] The charge transporting layer formed of such a polymer havingelectron-donating group or the polymer having the cross-linked structureexhibit excellent wear resistance. The charge potential (unexposed partpotential) is generally constant in electrophotographic process.Accordingly, when the surface layer of the photoconductor wears out inrepeated use, the field intensity applied on the photoconductorincreases as much. Since toner deposition on the background of imagesincreases with rise in the field intensity, the high wear resistance ofthe photoconductor is advantageous to prevent such phenomenon. Thecharge transporting layer formed by a polymer having electron-donatinggroup exhibits excellent film forming property since the polymer itselfis a high molecular compound, and may be able to form a chargetransporting portion at high density, compared to the chargetransporting layer consisting of a low molecular dispersion-typepolymer, and is excellent in charge transporting ability. Therefore,high-speed response may be expected for photoconductors having thecharge transporting layer comprising high molecular charge transportingmaterial.

[0094] Known materials may be used for the polymer charge transportingmaterial, and, particularly, polycarbonates containing triarylaminestructure in the main chain and/or side chain are preferably used. Highmolecular charge transporting materials represented by the followinggeneral formulae (I)-(X) are particularly suitable. These materials willbe described using concrete examples.

[0095] <Compound Represented by General Formula (I)>

[0096] [wherein R₁, R₂, and R₃ each independently represent asubstituted or non-substituted alkyl group or halogen atom; R₄represents hydrogen atom or a substituted or non-substituted alkylgroup; R₅ and R₆ each represent a substituted or non-substituted arylgroup; o, p and q each independently represent an integer of 0-4; k andj represent compositions and are 0.1≦k≦1 and 0≦j≦0.9; n represents thenumber of repeated units and is an integer of 5-5000; and X representsan aliphatic divalent group, an alicyclic divalent group, or a divalentgroup represented by the following general formula (a):

[0097] {wherein R₁₀₁ and R₁₀₁ each independently represent a substitutedor non-substituted alkyl group, an aryl group, or a halogen atom; 1 andm each represent an integer of 0-4; Y represents a single bond, astraight, branched, or cyclic alkylene group having 1-12 carbon atoms,—O—, —S—, —SO—, SO₂—, —CO—, —CO—O—Z—O—CO— (wherein Z represents analiphatic divalent group), or a divalent group represented by thefollowing general formula (b):

[0098] (wherein p is an integer of 1-20; q is an integer of 1-2000; R₁₀₃and R₁₀₄ each represent a substituted or non-substituted alkyl group oraryl group), and R₁₀₁ and R₁₀₂; R₁₀₃ and R₁₀₄ may be mutually the sameor different.)]

[0099] <Compound Represented by General Formula (II)>

[0100] (wherein R₇ and R₈ each represent a substituted ornon-substituted aryl group, Ar₁, Ar₂, and Ar₃, which may be the same ordifferent, each represent an arylene group; and X, k, j and n are thesame as in the general formula (I)).

[0101] <Compound Represented by General Formula (III)>

[0102] (wherein R₉ and R₁₀ each represent a substituted ornon-substituted aryl group; Ar₄, Ar₅ and Ar₆, which may be the same ordifferent, each represent an arylene group; and X, k, j and n are thesame as in the general formula (I)).

[0103] <Compound Represented by General Formula (IV)>

[0104] (wherein R₁₁ and R₁₂ represent a substituted or non-substitutedaryl group; Ar₇, Ar₈ and Ar₉, which may be the same or different, eachrepresent an arylene group; and X, k, j and n are the same as in thegeneral formula (I)).

[0105] <Compound Represented by General Formula (V)>

[0106] (wherein R₁₃ and R₁₄ each represent a substituted ornon-substituted aryl group; Ar₁₀, Ar₁₁ and Ar₁₂, which may be the sameor different, each represent an arylene group; X₁ and X₂ each representa substituted or non-substituted ethylene group or a substituted ornon-substituted vinylene group; and X, k, j and n are the same as in thegeneral formula (I)).

[0107] <Compound Represented by General Formula (VI)

[0108] (wherein R₁₅, R₁₆, R₁₇, and R₁₈ each represent a substituted ornon-substituted aryl group; Ar₁₃, Ar₁₄, Ar₁₅, and Ar₁₆, which may be thesame or different, each represent an arylene group; Y₁, Y₂ and Y₃, whichmay be the same or different, each represent a single bond, asubstituted or non-substituted alkylene group, a substituted ornon-substituted cycloalkylene group, a substituted or non-substitutedalkylene ether group, oxygen atom, sulfur atom, or a vinylene group; andX, k, j and n are the same as in the general formula (I)).

[0109] <Compound Represented by General Formula (VII)>

[0110] (wherein R₁₉ and R₂₀ each represent hydrogen atom or asubstituted or non-substituted aryl group and may form a ring; Ar₁₇,Ar₁₈ and Ar₁₉, which may be the same or different, each represent anarylene group; and X, k, j and n are the same as in the general formula(I)).

[0111] <Compound Represented by General Formula (VIII)>

[0112] (wherein R₂₁ represents a substituted or non-substituted arylgroup; Ar₂₀, Ar₂₁, Ar₂₂, and Ar₂₃, which are the same or different, eachrepresent an arylene group; and X, k, j and n are the same as in thegeneral formula (I)).

[0113] <Compound Represented by General Formula (IX)>

[0114] (wherein R₂₂, R₂₃, R₂₄ and R₂₅ each represent a substituted ornon-substituted aryl group; Ar₂₄, Ar₂₅, Ar₂₆, Ar₂₇ and Ar₂₈, which maybe the same or different, each represent an arylene group; and X, k, jand n are the same as in the general formula (I)).

[0115] <Compound Represented by General Formula (X)>

[0116] (wherein R₂₆ and R₂₇ each represent a substituted ornon-substituted aryl group; Ar₂₉, Ar₃₀ and Ar₃₁, which may be the sameor different, each represent an arylene group; and X, k, j and n are thesame as in the general formula (I)).

[0117] These high molecular charge transporting materials may be usedindependently or in combination of two or more of other high molecularcharge transporting materials. Also a low molecular charge transportingmaterial can be used together. As other polymers havingelectron-donating group, copolymers, block polymers, graft polymers,star polymers of known monomers, or cross-linked polymers havingelectron-donating group as disclosed in Japanese Patent ApplicationLaid-Open Nos. 3-109406, 2000-206723, and 2001-34001 may be used.

[0118] In the photoconductor of the present invention, a plasticizer orleveling agent may be added to the charge transporting layer 37. As theplasticizer, a one generally used as resin plasticizer such as dibutylphthalate, dioctyl phthalate or the like is usable as it is, and theappropriate use quantity thereof is about 0-30 wt % to the binder resin.As the leveling agent, a silicone oil such as dimethyl silicone oil,methylphenyl silicone oil, etc. or a polymer or oligomer havingperfluoroalkyl group on the side chain is used, and the appropriateusing quantity thereof is 0-1 wt % to the binder resin.

[0119] When the photosensitive layer has a single-layer structure 33, aphotosensitive layer having at least the above-mentioned chargegenerating material dispersed in the binder resin can be used. Thesingle-layer photosensitive layer is formed by dissolving or dispersingthe charge generating material and the binder resin to an appropriatesolvent, and applying the resulting solution and dried. Also, thephotosensitive layer may be formed into function separating type byadding the charge transporting material. Further, a plasticizer, aleveling agent, an antioxidant and the like may be added as required.

[0120] As the binder resin, the binder resins described in thedescription of the charge transporting layer 37 may be used as they areand also in combination with the binder resins described in thedescription for the charge generating layer 35. Of course, the highmolecular charge transporting materials described above may also beused. The preferred amount of the charge generating material against 100parts by weight of the binder resin is determined at 5-40 parts byweight, and the quantity of the charge transporting material ispreferably determined at 0-190 parts by weight, more preferably, 50-150parts by weight. The single-layer photosensitive layer can be formed byapplying a coating solution obtained by dispersing the charge generatingmaterial and the binder resin with the charge transporting material ifnecessary, using a solvent such as tetrahydrofurane, dioxane,dichloroethane, cyclohexane, etc. in a dispersing machine or the like bymeans of dipping coating, spray coating, bead coating, nozzle coating,spinner coating, ring coating, or the like. The appropriate thickness ofthe single layer photosensitive layer is about 5-100 μm.

[0121] In the photoconductor of the present invention, an undercoatlayer (not shown in the drawings) may be provided between the conductivesupport 31 and the photosensitive layer. The undercoat layer isgenerally mainly comprised of a resin. The resin desirably has highresistance to general organic solvents when application of thephotoconductive layer onto the resin in a form of solvent is considered.Such resins include a water-soluble resin such as polyvinyl alcohol,casein and sodium polyacrylate; an alcohol-soluble resin such ascopolymerized nylon and methoxy methylated nylon; a curable resinforming a three-dimensional mesh structure such as polyurethane,melamine resin, phenolic resin, alkyd-melamine resin and epoxy resin;and the like. Further, a fine finely powdered pigment of a metal oxidesuch as titanium oxide, silica, alumina, zirconium oxide, tin oxide,indium oxide, etc., may be added to the undercoat layer to preventmoire, reduction of residual potential, and the like.

[0122] The undercoat layer can be formed using an appropriate solventand coating method as mentioned above in the description of thephotosensitive layer. Further, as the undercoat layer of the presentinvention, a silane coupling agent, a titanium coupling agent, achromium coupling agent or the like may be used. Moreover, for theundercoat layer of the present invention, a substance having Al₂O₃provided by anodic oxidation and a substance having organics such aspolyparaxylene (parylene) or the like or inorganics such as SiO₂, SnO₂,TiO₂, ITO, CeO₂, and the like provided by vacuum thin film formingmethod may also be used including the ones that are known. Theappropriate thickness of the undercoat layer is 0-5 μm.

[0123] In the photoconductor of the present invention, the protectivelayer 39 is provided on the photosensitive layer for the purpose ofprotecting the photosensitive layer. The materials used for theprotective layer include ABS resin, ACS resin, olefin-vinyl monomercopolymer, chlorinated polyether, allyl resin, phenolic resin,polyacetal, polyamide, polyamide-imide, polyacrylate, polyallylsulfone,polybutylene, poly(butylene terephthalate), polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylicresin, polymethyl pentene, AS resin, butadiene-styrene copolymer,polyurethane, polyvinyl chloride, polyvinylidene chloride, epoxy resinand the like.

[0124] In order to improve wear resistance, a filler may be added to theprotective layer 39. Such fillers include, for example, inorganicfillers represented by, titanium oxide, silica, alumina, tin oxide,zirconium oxide, potassium titanate, and the like; and, organic fillersrepresented by, spherical ones of fluorine resin such aspolytetrafluoroethylene, cross-linked silicone resin such ascross-linked dimethylsiloxane, melamine resin, benzoguanamine resin,styrene-divinylbenzene copolymer, and the like. Among them, fillershaving effect of reducing surface energy of the surface ofphotoconductor may be suitably used. Examples thereof include particlesof fluorine resin and silicon resin. When the surface energy of thephotoconductor using such fillers is reduced, effect of the presentinvention will show more clearly.

[0125] A filler having high electric insulating property may beappropriately (specific resistance 1×10¹⁰ Ω·cm or more) used. Of suchfillers, α-type alumina having hexagonal minute structure having highinsulating property, high thermal stability and high wear resistance isparticularly useful from the standpoint of suppressing image blurringand improving wear resistance.

[0126] The specific resistance of the filler of the present invention isdefined as follows. Since a powder such as filler have specificresistance value varied depending on the rate of filling, the specificresistance value must be measured under fixed condition. In the presentinvention, the resistance rate of the fillers were measured using adevice having the same structure as measuring devices shown in JapanesePatent Application Laid-Open Nos. 5-94049 (FIG. 1) and 5-113688 (FIG.1), and the resulting values were used. In the measuring device, theelectrode area is 4.0 cm². A load of 4 kg is applied to one electrodefor 1 min prior to measurement, and the sample quantity is adjusted sothat the electrode-to-electrode distance is 4 mm. The measurement isperformed in the loading state of the weight (1 kg) of the upperelectrode with an applied voltage of 100V. The measurement was performedusing HIGH RESISTANCE METER (YOKOGAWA HEWLETT-PACKERD) for the region of10⁶ Ω·cm or more and using a digital multimeter (FLUKE) for the regionbelow. The resulting specific resistance values are determined as thespecific resistance value mentioned in the present invention.

[0127] The volume average particle diameter of the filler used ispreferably set to the range of 0.1-2 μm, and preferably to the range of0.3-1 μm. When the average particle diameter is too small, the wearresistance cannot be sufficiently exhibited, and when it is too large,the surface property of the coating is deteriorated, or the coatingitself cannot be formed.

[0128] The average particle diameter of the filler in the presentinvention means a volume average particle diameter as long as it is notspecially described, and determined using an ultracentrifugal automaticparticle diameter distribution measuring device: CAPA-700 (made byHORIBA). It is calculated as a particle diameter (Median series)corresponding to 50% of the cumulative distribution. The respectivestandard deviation of simultaneously measured particles is preferably 1μm or less. When the standard deviation exceeds this range, the particlediameter distribution is too large to clearly obtain an effect of thepresent invention.

[0129] The filler can be surface-treated with at least one kind ofsurface treatment agents, and this treatment is preferred from theviewpoint of the dispersibility of the filler. Since the deteriorationin dispersibility of the filler causes not only the rise of residualpotential but also the deterioration of transparency of the coating, thegeneration of a paint film defect, all of which might develop into aserious problem obstructing the higher durability or higher imagequality. As the surface treatment agent, all surface treatment agentsused in the past may be used. Among them, a surface treatment agentcapable of keeping the insulating property of the filler is preferred.For example, a titanate-based coupling agent, an aluminum-based couplingagent, a zircoaluminate-based coupling agent, a higher fatty acid andthe like, or mixing thereof with a silane coupling agent; Al₂O₃, TiO₂,ZrO₂, silicone, aluminum stearate and the like, or mixing thereof arepreferable from the standpoint of dispersibility of filler and imageblurring. The treatment with the silane coupling agent improvesgeneration of image blurring, but the affect can often be suppressed bymixing the above-mentioned surface treatment agent with the silanecoupling agent.

[0130] The surface treatment amount is varied depending on the averageprimary particle diameter of the filler used, but preferably 3-30 wt %,and more preferably, 5-20 wt %. When the surface treatment amount isless than these ranges, the effect of dispersing the filler cannot beobtained, and an excessively large amount thereof causes a remarkablerise of residual potential. The filler materials are used independentlyor in combination of two or more. The surface treatment amount of thefiller is defined by the weight ratio of the surface treatment agentused to the filler quantity as described above.

[0131] The filler material can be dispersed using a appropriatedispersing machine. From the viewpoint of the permeability of theprotective layer, the filler used is preferably dispersed to the primaryparticle level to minimize generation of aggregate.

[0132] A charge transporting material is preferably added to theprotective layer 39 for the purpose of reducing the residual potential,improving the photosensitivity and improving the high-speedresponsiveness. As the charge transporting material to be added, the lowmolecular charge transporting materials described in the description forthe charge transporting layer 35 may be used. The above-mentioned highmolecular charge transporting materials are also further preferably usedfrom the viewpoint of improvement in wear resistance, high-speedresponsiveness, and the like. When the low molecular charge transportingmaterial is used as the charge transporting material, a concentrationgradient may be provided in the protective layer. To improvement thewear resistance, reduction of concentration at the surface is aneffective method. The concentration mentioned herein means the ratio ofthe weight of the low molecular charge transporting material to thetotal weight of all the materials constituting the protective layer, andthe concentration gradient means to provide a gradient in theconcentration so that the concentration becomes low near the surfaceunder the weight ratio mentioned above. The use of the high molecularcharge transporting material is extremely advantageous to improve thedurability of the photoconductor.

[0133] The suppression of the rise in residual potential can be realizedby adding an organic compound having acid value of 10-400 (mgKOH/g). Theacid value mentioned herein is defined by the milligram number ofpotassium hydroxide required for the neutralization of the free fattyacid contained in 1 g. As the organic compound having acid value of10-400 (mgKOH/g), all organic compounds having acid value of 10-400mgKOH/g) such as generally known organic fatty acid, high acid valueresin, and the like may be used. However, since an extremely lowmolecular organic acid or acceptor has the possibility to significantlydeteriorate dispersibility of the filler, the effect caused by reductionin residual potential often cannot be obtained at satisfying level.Accordingly, to reduce the residual potential of the photoconductor andimprove the dispersibility of the filler, a low molecular polymer, aresin, a copolymer and the like, and mixtures thereof are preferablyused. Such an organic compound preferably has a linear structure havingless three-dimensional obstruction. In order to improve thedispersibility, it is important to impart affinity to both the fillerand the binder resin, and a material with serious three-dimensionalobstruction deteriorates the dispersibility by the deterioration of itsaffinity, causing many problems as described above.

[0134] As the organic compound having acid value of 10-400 (mgKOH/g),polycarboxylic acid is preferably used. As the polycarboxylic acid, allof organic compounds containing carboxylic acid such as polyester resin,acrylic resin, a copolymer using acrylic acid or methacrylic acid,styrene-acryl copolymer, etc. and derivatives thereof, which arecompounds having a structure containing carboxylic acid in a polymer orcopolymer, can be used. These materials can be used in combination oftwo or more, with effect. As necessary, these materials are mixed withan organic fatty acid, whereby the dispersibility of the filler and theeffect of reducing residual potential often improves.

[0135] The added amount of the organic compound having acid value of10-400 (mgKOH/g) is set to 0.01-50 wt %, preferably 0.1-20 wt % to thefiller contained. More preferably, it is set to a necessary minimumquantity. When the amount added is larger than what is required, adverseeffect such as image blurring often appears, and when the amount addedis too small, the effect of reducing residual potential cannot beobtained enough. The preferable acid value of the organic compound is10-400 mgKOH/g, and more preferably 30-200 mgKOH/g. When the acid valueis higher than what is required, the resistance is excessively reducedto induce image blurring, and when the acid value is too low, thenecessary amount to be added increases, effect of reducing residualpotential could not be obtained. It is thus necessary to determine theacid value of the organic compound based on balance with amount added.The acid value of the organic compound does not directly affect thereduction of residual potential. This effect is greatly affected by thestructure or molecular weight of the organic compound used, thedispersibility of the filler or the like.

[0136] For the purpose of reducing the surface energy of thephotoconductor, it is desirable to add various additives to theprotective layer to reduce the surface energy. The additives include,for example, silicone oil, fluorine resin, silicone-based resin, and thelike. Among them, silicone oil is most suitably used.

[0137] The protective layer of the photoconductor is generally opticallytransparent, because the protective layer needs to transmit an imagelight. Accordingly, the material added to reduce the surface energy mustbe compatible with the material forming the protective layer. Of course,there is a case when such material is optically transparent when it ispresent as a fine particle smaller than the wavelength of the imagelight, but it is rather difficult to cover the whole visible light area.It is necessary to take the dispersion stability of the coating solutioninto consideration for the production, resulting in a complicateddesign. From such a point, a “dissolved” state (the state dissolvedthrough a solvent) is preferable as the state of the coating solution.The silicone oil in the present invention is selected from such aviewpoint, and preferably used.

[0138] The outermost layer of the photoconductor is a protective layerlaminated for the purpose of protecting the photosensitive layer. Whenthe surface energy is reduced by adding the silicone oil to theprotective layer, the purpose of the present invention is moreeffectively accomplished. Considering the purpose of the presentinvention, such effect should be obtained over a long period of time.Considering this point, the silicone oil is often insufficient from aquantitative point in the state compatible with the materialconstituting the protective layer as described above. In such a case,the continuity of the effect can be improved by adding a quantityexceeding the limit of compatibility. The silicone oil is naturallyprecipitated in the layer. The silicone oil is generally precipitated inthe inner portion of the protective layer [not only in the protectivelayer, but also in the photosensitive layer formed on the inside thereof(the side closer to the support)] and consequently laid in the statestocked within the photoconductor (breezed out to the surface asnecessary).

[0139] Although the protective layer is apparently clouded white in thiscase, and the image light seems not to advance to the photoconductorinner portion, the degree of scattering of the image light haswavelength dependency, so that the closer the image light shifts to thelonger wave side, the more image light advances. Actually, the imagelight is transmitted nearly 100% in a LD region (red to near infrared),and hardly causes any trouble also in a visible range (blue-red). Thedegree of scattering is remarkable in an ultraviolet portion havingshort wavelength. However, the light of this region is not used much asthe image light in a general electrophotographic process, and frequentlycut because it is harmful to the photoconductor, and this is out of thequestion.

[0140] The particle or droplet size (or diameter) of the silicone oilprecipitated in the protective layer is one factor affecting imagecharacteristics. As a result of examinations on the present invention,it is found that a diameter 1 μm or less does not affect a generalimage. A size larger than this often affect portion of the image. Thisis assumed to be attributed to that the optical carrier formed withinthe photoconductor cannot cross over the silicone oil portion having nocarrier transportability. Although even about 1 μm might affect whenobserved from an extremely micro viewpoint, it is assumed that theinfluence caused by about 1 μm cannot be observed from the points of theparticle diameter of toner used in the general electrophotographicprocess, the reproducibility in development and transfer, and the like.The size of the particle or droplet is related also to the thickness ofthe protective layer. As a result of examination, it was found that asize smaller than ⅕ of the thickness has no affect on the image. Thereason for this is assumed to be caused by that the size of this degreedo not obstruct the surface-directional (surface of photoconductor orsupport surface) progress of the optical carrier in addition to theabove-mentioned reason.

[0141] In addition to the protective layer, the silicone oil may beadded to a layer (photosensitive layer) closer to the support than it.When it is added in a quantity exceeding the compatibility, theinternally accumulated form is often more advantageous, it is desirableto select effective means by confirmed in experiment. In this case,also, the silicone oil is often breezed to the protective layerreversely to the above, but this is not a particular problem. Asdescribed above, it is also breezed out to the protective layer side inrepeated uses.

[0142] As the silicone oil used in the present invention, known siliconeoils, for example, dimethyl silicone oil, methylphenyl silicone oil,methyl hydrogen polysiloxane, cyclic dimethyl polysiloxane,alkyl-modified silicone oil, polyether-modified silicone oil,alcohol-modified silicone oil, fluorine-modified silicone oil,amino-modified silicone oil, mercapto-modified silicone oil,epoxy-modified silicone oil, carboxyl-modified silicone oil, higherfatty acid-modified silicone oil, higher fatty acid-containing siliconeoil and the like may be used, and any one capable of reducing thesurface energy of the outermost layer may also be used. Among them,methylphenyl silicone oil can be particularly effectively used.

[0143] To form the protective layer, a general application method may beadapted. The appropriate thickness of the protective layer is about0.1-10 μm.

[0144] In the photoconductor of the present invention, an intermediatelayer (not shown in the drawings) may be provided in between thephotosensitive layer and the protective layer. For the intermediatelayer, a binder resin is generally used as the main component. Thebinder resins include polyamide, alcohol soluble nylon, water-solublepolyvinyl butyral, polyvinyl alcohol and the like. To form theintermediate layer, a general application method may be adapted asdescribed above. The appropriate thickness of the intermediate layer isabout 0.05-2 μm.

[0145] In the present invention, in order to improve the environmentalresistance, particularly, to prevent the reduction in sensitivity andthe rise of residual potential, an antioxidant, a plasticizer, alubricant, an ultraviolet absorber, a low molecular charge transportingmaterial, and a leveling agent may be added to each layer. Typicalmaterials for these compounds are described below.

[0146] The antioxidants which may be added to each layer include thosedescribed below, but not limited to these.

[0147] (a) Phenolic Compounds

[0148] 2,6-Di-t-butyl-p-cresol, butylated hydroxyanisole,2,6-di-t-butyl-4-ethylphenol,n-octadecyl-3-(4′-hydroxy-3′,5′-di-ti-butylphenol),2,2′-methylene-bis-(4-methyl-6-t-butylphenol),2,2′-methylene-bis-(4-ethyl-6-t-butylphenol),4,4′-thiobis-(3-methyl-6-t-butylphenol),

[0149] 4,4′-butylidenebis-(3-methyl-6 -t-butyl phenol),1,1,3-tris-(2-methyl-4-hydroxy-5-t-buthylphenyl)butane,1,3,5-trimethyl-2,4,6-tris(3,5-di-ti-buthylphenyl)butane,1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,tetraquis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane,bis[3,3′-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid]glycol ester,tocopherol, and the like.

[0150] (b) Paraphenylenediamines

[0151] N-Phenyl-N′-isopropyl-p-phenylenediamine,N,N′-di-sec-butyl-p-phenylenediamine,N-phenyl-N-sec-butyl-p-phenylenediamine,N,N′-di-isopropyl-p-phenylenediamine,N,N′-dimethyl-N,N′-di-t-butyl-p-phenylenediamine, and the like.

[0152] (c) Hydroquinones

[0153] 2,5-Di-t-octylhydroquinone, 2,6-didodecylhydroquinone,2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone,2-t-octyl-5-methylhydroquinone, 2-(2-octadecenyl)-5-methylhydroquinone,and the like.

[0154] (d) Organic Sulfur Compounds

[0155] Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate,ditefradecyl-3,3′-thiodipropionate, and the like

[0156] (e),Organic Phosphor Compounds

[0157] Triphenyl phosphine, tri(nonylphenyl)phosphine,tri(dinonylphenyl)phosphine, tricresyl phosphine,tri(2,4-dibutylphenoxy)phosphine and the like.

[0158] The plasticizers which may be added to each layer include thosedescribed below, bur are not limited to these.

[0159] (a) Phosphate-Based Plasticizers

[0160] Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate,octyldiphenyl phosphate, trichloroethyl phosphate, cresylphenylphosphate, tributyl phosphate, tri-2-ethylhexylphosphate, triphenylphosphate, and the like.

[0161] (b) Phthalate-Based Plasticizers

[0162] Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate,dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate,diisooctyl phthalate, di-n-octyl phthalate, dinonyl phthalate,diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate,tridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, butyllauryl phthalate, methyloleyl phthalate, octyldecyl phthalate, dibutylfumarate, dioctyl fumarate, and the like.

[0163] (c) Aromatic Carboxylate-Based Plasticizers

[0164] Trioctyl trimeritate, tri-n-octyl trimeritate, octyl oxybenzoate,and the like.

[0165] (d) Aliphatic Dibasic Acid Ester-Based Plasticizers

[0166] Dibutyl adipate, di-n-hexyl adipate, di-w-ethylhexyl adipate,di-n-octyl adipate, n-octyl-n-decyl adipate, diisodecyl adipate,dicapryl adipate, di-2-ethylhexyl azelate, dimethyl sebacate, diethylsebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexylsebacate, di-2-ethoxyetyl sebacate, dioctyl succinate, diisodecylsuccinate, dioctyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate,and the like.

[0167] (e) Fatty Acid Ester Derivatives

[0168] Butyl oleate, glycerin monooleate, methyl acetyl ricinoleate,pentaerythritol ester, dipentaerythritol hexa ester, triacetine,tributyrine, and the like.

[0169] (f) Oxy Acid Ester-Based Plasticizers

[0170] Methyl acetyl ricinoleate, butyl acetyl ricinoleate,butylphthalyl butyl glycolate, tributyl acetyl citrate, and the like.

[0171] (g) Epoxy Plasticizers

[0172] Epoxidized soybean oil, epoxidized linseed oil, butyl epoxystearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxystearate, diocyl epoxy hexahydrophthalate, decyl epoxyhexahydrophthalate, and the like.

[0173] (h) Dihydric Alcohol Ester-Based Plasticizers

[0174] Diethylene glycol dibenzoate, triethylene glycoldi-2-ethylbutylate, and the like.

[0175] (i) Chlorinated Plasticizers

[0176] Chlorinated paraffin, chlorinated diphenyl, chlorinated fattyacid methyl, methoxy chlorinated fatty acid methyl, and the like.

[0177] (j) Polyester-Based Plasticizers

[0178] Polypropylene adipate, polypropylene sebacate, polyester,acetylated polyester, and the like.

[0179] (k) Sulfonic Acid Derivatives

[0180] p-Toluene sulfonamide, o-toluene sulfonamide, p-toluenesulfonethylamide, o-toluene sulfonethylamide, toluenesulfone-N-ethylamide, p-toluenesulfone-N-cyclohexylamide, and the like.

[0181] (l) Citric Acid Derivatives

[0182] Triethyl citrate, triethyl acetyl citrate, tributyl citrate,tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, n-octyl acetylcitrate, and the like.

[0183] (m) Others

[0184] Tertiary phenyl, partially hydrogenated tertiary phenyl, camphor,2-nitrodiphenyl, dinonylnaphthalene, methyl abietate, and the like.

[0185] The lubricants which may be added to each layer include, forexample, those described below, bur are not limited to these.

[0186] (a) Hydrocarbon-Based Compounds

[0187] Liquid paraffin, paraffin wax, microwax, low polymerizedpolyethylene, and the like.

[0188] (b) Fatty Acid-Based Compounds

[0189] Lauric acid, myristic acid, palmitic acid, stearic acid,alachidic acid, behenic acid, and the like.

[0190] (c) Fatty Amide-Based Compounds

[0191] Stearylamide, palmitylamide, oleinamide, methylenebisstealoamide, ethylene bissteraloamide, and the like.

[0192] (d) Ester-Based Compounds

[0193] Lower alcohol ester of fatty acid, polyhydric alcohol ester offatty acid, fatty acid polyglycol ester, and the like.

[0194] (e) Alcohol-Based Compounds

[0195] Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethyleneglycol, polyglycerol, and the like.

[0196] (f) Metal Soap

[0197] Lead stearate, cadmium stearate, barium stearate, calciumstearate, zinc stearate, magnesium stearate, and the like.

[0198] (g) Natural Wax

[0199] Carnauba wax, candelilla wax, beeswax, permaceti wax, Chinesewax, montan wax, and the like.

[0200] (h) Others

[0201] Silicone compound, fluorine compound, and the like.

[0202] The ultraviolet absorbers which may be added to each layerincludes, for example, those described below, but not limited to these.

[0203] (a) Benzophenone-Based Ones

[0204] 2-Hydroxybenzophenone, 2,4-dihydroxybenzophenone,2,2′,4-trihydroxybenzophenone, 2,2′,4,4′-tetrahydroxybenzophonone,2,2′-dihydroxy-4-methoxybenzophenone, and the like.

[0205] (b) Salicylate-Based Ones

[0206] Phenyl salicylate,2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, and the like.

[0207] (c) Benzotriazol-Based Ones

[0208] (2′-Hydroxyphenyl)benzotriazol,(2′-hydroxy-5′-methylphenyl)benzotriazol,(2′-hydroxy5′-methylphenyl)benzotriazol,(2′-hydrox-3′-tertiarybutyl-5′-methylphenyl)-5-chlorobenzotr iazol, andthe like.

[0209] (d) Cyano Acrylate-Based One

[0210] Ethyl-2-cyano-3,3′-diphenylacrylate,methyl-2-carbomethoxy-3-(paramethoxy)acrylate, and the like.

[0211] (e) Quencher (Metal Complex Salt-Based)

[0212] Nickel{2,2′-thiobis(4-t-octyl)phenolate}normal butylamine, nickeldibutyl dithiocarbamate, nickel dibutyl dithiocarbamate, cobaltdicyclohexyl dithiophosphate, and the like.

[0213] (f) HALS (Hindered Amine)

[0214] Bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,1-[2-{3-(3,5-di-butyl-4-hydroxhphenyl)propionyloxy}ethyl]-4-{3-(3,5-di-ti-butyl-4-hydroxyphenyl)propionyloxy}ethyl]-2,2,6,6-tetramethylpyridine,8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro[4,5]undecane-2,4-dione, 4-benzoiloxy-2,2,6,6-tetramethylpiperidine, and thelike.

[0215] The electrophotographic device of the present invention is thendescribed in detail using the drawings.

[0216]FIG. 4 is a schematic view showing one example of anelectrophotographic device according to the present invention, and amodified example as described below also belongs to the category of thepresent invention.

[0217] In FIG. 4, a photoconductor 1 comprises a photosensitive layerand a protective layer (outermost layer) containing a filler provided ona conductive support. The photoconductor 1 has a drum shape, but it mayhave a sheet-like or endless belt-like shape.

[0218] An charging member 8 is arranged in contact with or adjacently tothe photoconductor. The charging member is preferably used with lessgeneration of ozone or nitrogen oxide forming the generation source of alow resistance material, compared with the corona charging by a chargerrepresented by a corotron or scorotron. Particularly, a non-contactcharge roller having the charging member adjacently arranged to thesurface of photoconductor in 200 μm or less (preferably, 100 μm or less)is preferably usable with extremely little contamination of the chargingmember in repeated uses.

[0219] The adjacently arranged charging member is of a type adjacentlyarranged in a non-contact state so as to have a gap of 200 μm or lessbetween the surface of photoconductor and the charging member surface.It is discriminated from known chargers represented by corotron andscorotron by the distance of gap. The adjacently arranged chargingmember of the present invention may have any shape if it has a mechanismcapable of appropriately controlling the gap with the surface ofphotoconductor. For example, the rotating shaft of the photoconductorcan be mechanically fixed to the rotating shaft of the charging memberand arranged so as to have a appropriate gap. Particularly, the gap canbe stably kept with an easy method by using an charge roller-shapedcharging member, arranging gap-forming members on both ends of thenon-image forming portion of the charging member, and allowing onlythese parts to abut on the surface of photoconductor to arrange an imageforming area in no contact; or by arranging the gap-forming members onboth ends of the non-image forming portion of the photoconductor andallowing only these portions to abut on the charging member surface toarrange the image forming area in no contact. Particularly, the methodsdescribed in Japanese Patent Application Nos. 13-211448 and 13-226432may suitably be used. One example of an adjacent charging mechanismhaving the gap-forming members arranged on the charging member side isshown in FIG. 5. In FIG. 5, denoted at 29 is a photoconductor, 30 is acharging roller, 31 is a gap-forming member, 32 is a metal shaft, 33 isan image forming area, and 34 is a non-image forming area.

[0220] A pre-transfer charger 12, a transfer charger, a separationcharger, and a pre-cleaning charger 17 are arranged as necessary, andknown means including a corotron, a scorotron, a solid state charger andan charge roller may be used. In charging the photoconductor by thecharging member, the photoconductor is charged by the electric fieldhaving an AC component superimposed on a DC component in the chargingmember, whereby the uneven charge can be effectively reduced (FIG. 4).

[0221]FIG. 6 is a schematic view for illustrating anotherelectrophotographic device according to the present invention, and amodified example as described below also belongs to the category of thepresent invention.

[0222] In FIG. 6, denoted at 1C, 1M, 1Y and 1K are drum-likephotoconductors, and the photoconductors 1C, 1M, 1Y and 1K are rotatedin the direction shown by the arrow in the drawing. At least chargingmembers 2C, 2M, 2Y and 2K, developing members 4C, 4M, 4Y and 4K, andcleaning members 5C, 5M, 5Y and 5K are arranged around them,respectively. The charging members 2C, 2M, 2Y and 2K constitute ancharging device for uniformly charging the surface of photoconductor.Laser beams 3C, 3M, 3Y and 3K from exposing members not shown in thedrawings between the charging members 2C, 2M, 2Y and 2K and thedeveloping members 4C, 4M, 4Y and 4K are emitted to the surface ofphotoconductors to form electrostatic latent images on thephotoconductors 1C, 1M, 1Y and 1K. Four image forming elements (units)6C, 6M, 6Y and 6K having the photoconductors 1C, 1M, 1Y and 1K as coresare juxtaposed along a transfer carrying belt 10 that is a transfermaterial carrying means. The transfer carrying belt 10 abuts on thephotoconductors 1C, 1M, 1Y and 1K between the developing members 4C, 4M,4Y and 4K and the cleaning members 5C, 5M, 5Y and 5K of each imageforming unit 6C, 6M, 6Y and 6K, respectively, and transfer brushes 11C,11M, 11Y and 11K for applying a transfer bias are arranged on the side(reverse side) corresponding to the photoconductor-side back of thetransfer carrying belt 10. Each image forming element 6C, 6M, 6Y or 6Khas the same structure except that the color of toner in the developingdevice is differed, and the black toner image forming photoconductor 1Krelated to the present invention is differed in crude pipe diameter fromother photoconductors (the circumference of the photoconductor 1K islonger than those of the photoconductors 1C, 1M, and 1Y).

[0223] In the color electrophotographic device having the structureshown in FIG. 6, an image forming operation is performed as follows. Ineach image forming element 6C, 6M, 6Y or 6K, each photoconductor 1C,1M_(,) 1Y or 1K is charged by the charging member 2C, 2M, 2Y or 2Krotating in the direction shown by the arrow (the co-rotating directionwith the photoconductor), and an electrostatic latent imagecorresponding to the image of each color to be formed is formed by laserbeam 3C, 3M, 3Y or 3K in an exposing portion. The latent image isdeveloped by each developing member 4C, 4M, 4Y or 4K to form a tonerimage. The developing members 4C, 4M, 4Y and 4K perform development withtoners of C (cyan), M (magenta), Y (yellow) and K (black), respectively,and the toner images of each color formed on the four photoconductors1C, 1M, 1Y and 1K are overlapped on a transfer paper. The transfer paper7 is fed from a tray by a feed roll 8, once stopped in a pair of resistrollers 9, and then sent to the transfer carrying belt 10 at a timingmatched to the image formation onto the photoconductor. The transferpaper 7 held on the transfer carrying belt 10 is carried, and thetransfer of each color toner image is preformed in a contact position(transfer portion) with each photoconductor 1C, 1M, 1Y and 1K. The tonerimage on the photoconductor is transferred onto the transfer paper 7 bythe electric field created by the potential difference between thetransfer bias applied to the transfer brushes 11C, 11M, 11Y and 11K andthe photoconductors 1C, 1M, 1Y and 1K. The recording paper 7 having thefour color toner images overlapped thereon through the four transferportions is carried to a fixing device 12 to fix the toner, and thendischarged to a discharge portion not shown in the drawings. Theresidual toner left on each photoconductor 1C, 1M, 1Y or 1K withoutbeing transferred in the transfer portion is recovered by cleaningdevices 5C, 5M, 5Y and 5K. In the example of FIG. 6, the image formingelements are arranged in the order of C (cyan), M (magenta), Y (yellow)and K (black) from the transfer carrying directional upstream side tothe downstream side, but the order of colors may be optionally setwithout being limited to this order. In the formation of a document ofonly black, it particularly effective for the present invention toprovide a mechanism for stopping the image forming elements 6C, 6M and6Y other than the black.

[0224] A member for supplying zinc stearate onto the surface ofphotoconductor, which is not shown in the drawings, may be furtherprovided. The supply of the zinc stearate onto the surface ofphotoconductor allows the filming suppression in a state withsatisfactory wear resistance, and further effective to suppress theimage flowing or ununiformity of halftone while retaining the wearresistance, in the electrophotographic process equipped with thephotoconductor, by repeating the toner adhesion and the toner recoveringoperation in the cleaning portion at the non-image forming time. Tosupply the zinc stearate, it is an extremely effective means to includethe zinc stearate in the developer (toner) present in the developingportion.

[0225] When the quantity of the zinc stearate supplied onto thephotoconductor is too large, the output quantity onto the transferoutput image is increased to unpreferably cause a fixing failure. Whenthe friction coefficient of the surface of photoconductor lowers toabout 0.1 by the excessive supply of zinc stearate, a reduction in imagedensity is unpreferably caused. For example, when the zinc stearate issupplied to the surface of photoconductor in the state included in thetoner, the content in the toner is preferably set to 0.1-0.2 wt %.

[0226] In the step for forming an image according to the presentinvention, the suppression of the filming on the surface ofphotoconductor and the suppression of the adhesion or accumulation of aproduct by charging while retaining the wear resistance can be attainedby the toner adhesion to the photoconductor and the toner recoveringoperation in the cleaning portion at the time of non-image forming. Thisis assumed to be attributed to that it has a cleaning effect fordischarging various deposits on the photoconductor together with thetoner. For the toner adhesion and recovering operation, a toner adhesionquantity of about halftone and an operating time of about 30 second (inphotoconductor diameter 30 mm, linear speed 125 mm/s) are effective, andthe adhesion quantity and operating time exceeding them are notpreferable because the load to the cleaning portion and the tonerconsumption are increased. When the photoconductor diameter and linearvelocity are varied, the adhesion quantity and operating time may beappropriately adjusted so as to have the same operating condition as theabove.

[0227] The above-mentioned chargers are usable as the transfer means,and a one using a transfer belt as shown in FIG. 4 may suitably be used.

[0228] As light sources of an image exposure part 10, a charge removinglamp 7 and the like shown in FIG. 4, light emittion source such asfluorescent lamp, tungsten lamp, halogen lamp, mercury vapor lamp, lowpressure sodium lamp, light emitting diode (LED), semiconductor laser(LD), electroluminescence (EL) , and the like are generally used. Inorder to emit a light of desired wavelength, various filters such assharp cut filter, band pass filter, near infrared cut filter, dichroicfiler, interference filter, color temperature conversion filter and thelike may also be used.

[0229] Such light sources are provided in the step for transferring,charge removing process, cleaning process, or pre-exposure processjointly using photoirradiation in addition to the process shown in FIG.4, whereby light is applied to the photoconductor.

[0230] The toner developed on the photoconductor 1 by a developing unit11 shown in FIG. 4 is transferred to a transfer paper 14. This toner isnot entirely transferred thereto but partially left on thephotoconductor 1. Such a residual toner is removed from thephotoconductor with a cleaning blade 18. The cleaning is often performedusing only the cleaning blade, but a cleaning brush or the like mayoften be used. As the cleaning brush, known brushes including fur brush,magnetic fur brush and the like may be used.

[0231] In FIG. 4, numeral 13 indicates a resist roller, 15 a transferbelt, 16 a separation claw, and 18 a fur brush.

[0232] When a photoelectric photoconductor is positively (negatively)charged in an image exposure, a positive (negative) electrostatic latentimage is formed on the surface of photoconductor.

[0233] This is developed with a toner of negative (positive) polarity(detecting fine particle), whereby a positive image is formed, anddeveloped with a toner of positive (negative) polarity, whereby anegative image is formed.

[0234] A known method may be applied to such developing means, and aknown method may be used for charge removing means.

EXAMPLES

[0235] The present invention is more specifically described according topreparation examples and working examples, however the present inventionis not limited thereto. All numerals in the following formulationsdenote parts by weight.

Synthetic Example of Polyester Resin Synthetic Example 1

[0236] To a four-neck separable flask equipped with a stirrer, athermometer, a nitrogen inlet port, a falling capacitor and a coolingpipe were added 740 g ofpolyoxypropylene(2,2)-2,2-bis(4-hydroxyphenyl)propane, 300 g ofpolyoxyethylene(2,2)-2,2-bis(4-hydroxyphenyl)propane, 466 g of dimethylterephthalate, 80 g of isodecenyl succinic anhydride, and 114 g oftri-n-butyl 1,2,4-benzenetricarboxylate together with an esterificationcatalyst. These were reacted while raising the temperature to 210° C. atordinary pressure under nitrogen atmosphere in the first half and whilereducing the pressure at 210° C. with stirring in the latter half. Apolyester resin with acid value of 2.3 KOHmg/g, hydroxyl value of 28.0KOHmg/g, softening point of 106° C., and Tg of 62° C. was consequentlyobtained (hereinafter referred to as polyester resin A).

Synthetic Example 2

[0237] 725 g of polyoxypropylene(2,2)-2,2-bis(4-hydroxyphenyl)propane,165 g of polyoxyethylene(2,2)-2,2-bis(4-hydroxyphenyl)-propane, 500 g ofterephthalic acid, 130 g of isodecenyl succinic anhydride, and 170 g oftriisopropyl 1,2,4-benenetricarboxylate together with an esterificationcatalyst were added in the flask. These were reacted with the samedevice and the same method as in Synthetic Example 1, and a polyesterresin with acid value of 0.5 KOHmg/g, hydroxyl value of 25.0 KOHmg/g,softening point of 109° C., and Tg of 63° C. was obtained (hereinafterreferred to as polyester resin B).

Synthetic Example of Polyol Resin Synthetic Example 1

[0238] To a separable flask equipped with a stirrer, a thermometer, anitrogen inlet port, and a cooling pipe were added 378.4 g of lowmolecular bisphenol A type epoxy resin (number average molecular weight:about 360), 86.0 g of high molecular bisphenol A type epoxy resin(number average molecular weight: about 2700), 191.0 g of glycidylate ofbisphenol A type propylene oxide additive, 274.5 g of bisphenol F, 70.1g of p-cumyl phenol, and 200 g of xylene. The temperature was raised to70-100° C. under nitrogen atmosphere to add 0.1839 g of lithiumchloride, and then further raised to 160° C. to remove the xylene underreduced pressure. The resulting mixture was polymerized at a reactiontemperature of 180° C. for 6-9 hrs to obtain a polyol resin with acidvalue of 0.0 KOHmg/g, hydroxyl value of 70.0 KOHmg/g, softening point of109° C., and Tg of 58° C. (hereinafter referred to as polyol resin A).

Synthetic Example 2

[0239] Using the device of Synthetic Example 1, 205.3 g of low molecularbisphenol A type epoxy resin (number average molecular weight: about360), 54.0 g of high molecular bisphenol A type epoxy resin (numberaverage molecular weight: about 3000), 432.0 g of glycidylate ofbisphenol A type propylene oxide additive, 282.7 g of bisphenol F, 26.0g of p-cumyl phenol, and 200 g of xylene were added thereto. Thetemperature was raised to 70-100° C. under nitrogen atmosphere to add0.183 g of lithium chloride, and further raised to 160° C. to remove thexylene under reduced pressure. The resulting mixture was polymerized ata reaction temperature of 180° C. for 6-9 hrs to obtain a polyol resinwith acid value 0.0 of KOHmg/g, hydroxyl value of 58.0 KOHmg/g,softening point of 109° C., and Tg of 58° C. (hereinafter referred to aspolyol resin B).

Preparation Example of Parent Toner 1

[0240] Binder resin Polyester resin A 100 parts Coloring agentQuinacridone-based magenta pigment  4 parts Charge controlling Zinccompound of salicylic acid  4 parts agent

[0241] 1. The above starting materials were mixed by a Henschel mixer;

[0242] 2. melted and kneaded using a bus cokneader (made by BUS) set to120° C.;

[0243] 3. the kneaded matter was finely pulverized using a pulverizingmachine using a turbo mill (manufactured by TURBO KYOGYO) after cooling;and

[0244] 4. classified using a wind classifier to obtain a magenta parenttoner (a) having volume average particle diameter: 6.38 μm, and specificsurface area: 2.48 m²/g.

[0245] (Preparation Example of Product Toner 1)

[0246] To 100 parts of the parent toner (a) of Preparation Example ofParent Toner 1, 0.7 wt % of HDK 2000H (made by WACKER, BET specificsurface area: 140 m²/g) and 0.5 wt % of AEROSIL RX 50 (made by NIPPONAEROSIL, BET specific surface area: 50 m²/g) as silica, and 0.5 wt % ofMT 150 (made by TAYCA, BET specific surface area: 65 m²/g) as titaniawere added, and sufficiently mixed using a Henschel mixer (made byMITSUI MIIKE) to obtain an electrophotographic toner A.

[0247] (Preparation Example of Product Toner 2)

[0248] To 100 parts of the parent toner (a) of Preparation Example ofParent Toner 1, 0.5 wt % of TG-810G (made by CABOT, BET specific surfacearea: 230 m²/g) and 0.5 wt % of AEROSIL RX50 (made by NIPPON AEROSIL,BET specific surface area: 50 m²/g) as silica, and 0.5 wt % of MT 250(made by TAYCA, BET specific surface area; 65 m²/g) as titania wereadded, and sufficiently mixed using a Henschel mixer (made by MITSUIMIIKE) to obtain an electrophotographic toner B.

[0249] (Preparation Example of Product Toner 3)

[0250] To 100 parts of the parent toner (a) of Preparation Example ofParent Toner 1, 0.5 wt % of AEROSIL RX200 (made by NIPPON AEROSIL, BETspecific surface area: 200 m²/g) and 1.2 wt % of AEROSIL RX50 (made byNIPPON AEROSIL, BET specific surface area: 50 m²/g) as silica, and 0.5wt % of MT 150 (made by TAYCA, BET specific surface area; 65 m²/g) astitania were added, and sufficiently mixed using a Henschel mixer (madeby MITSUI MIIKE) to obtain an electrophotographic toner C.

[0251] (Preparation Example of Parent Toner 2) Binder resin Polyesterresin B 100 parts Coloring agent Quinacridone-based magenta pigment  4parts Charge controlling Chromium compound of salicylic acid  4 partsagent

[0252] 1. The above starting materials were mixed by a Henschel mixer;

[0253] 2. melted and kneaded using a bus cokneader (made by BUS) set to120° C.;

[0254] 3. the kneaded matter was finely pulverized using a pulverizingmachine using a turbo mill (manufactured by TURBO) after cooling; and

[0255] 4. classified using a wind classifier to obtain a magenta parenttoner (b) having volume average particle diameter: 6.69 μm, and specificsurface area: 2.34 m²/g.

[0256] (Preparation Example of Product Toner 4)

[0257] To 100 parts of the parent toner (b) of Preparation Example ofParent Toner 2, 0.7 wt % of HDK 2000H (made by WACKER, BET specificsurface area: 140 m²/g) and 0.5 wt % of AEROSIL RX50 (made by NIPPONAEROSIL, BET specific surface area: 50 m²/g) as silica, and 0.5 wt % ofMT 150 (made by TAYCA, BET specific surface area; 65 m²/g) as titaniawere added, and sufficiently mixed using a Henschel mixer (made byMITSUI MIIKE) to obtain an electrophotographic toner D.

[0258] (Preparation Example of Parent Toner 3) Binder resin Polyol resinA 100 parts Coloring agent Quinacridone-based magenta pigment  4 partsCharge controlling Zinc compound of salicylic acid  4 parts agent

[0259] 1. The above starting materials were mixed by a Henschel mixer;

[0260] 2. melted and kneaded using a bus cokneader (manufactured by BUS)set to 120° C.;

[0261] 3. the kneaded matter was finely pulverized using a pulverizingmachine using a jet flow after cooling; and

[0262] 4. classified using a wind classifier to obtain a magenta parenttoner (c) having volume average particle diameter: 5.36 μm, and specificsurface area: 4.12 m²/g.

[0263] (Preparation Example of Product Toner 5)

[0264] To 100 parts of the parent toner (c) of Preparation Example ofParent Toner 3, 1.0 wt % of AEROSIL RX50 (made by NIPPON AEROSIL, BETspecific surface area: 50 m²/g) as silica, and 0.5 wt % of MT 150 (madeby TAYCA, BET specific surface area; 65 m²/g) as titania were added, andsufficiently mixed using a Henschel mixer (made by MITSUI MIIKE) toobtain an electrophotographic toner E.

[0265] (Preparation Example of Product Toner 6)

[0266] To 100 parts of the parent toner b of Preparation Example ofParent Toner 2, 1.0 wt % of TB-810G (made by CABOT, BET specific surfacearea: 230 m²/g) and 1.8 wt % of AEROSIL RX50 (made by NIPPON AEROSIL,BET specific surface area: 50 m²/g) as silica, and 0.5 wt % of MT 150(made by TAYCA, BET specific surface area; 65 m²/g) as titania wereadded, and sufficiently mixed using a Henschel mixer (made by MITSUIMIIKE) to obtain an electrophotographic toner F.

[0267] (Preparation of Photoconductor (a))

[0268] An undercoat layer coating solution, charge generating layercoating solution, and charge transporting layer coating solution havingthe following compositions were successively applied onto an aluminumcylinder (material: JIS 1050) 90 mm in diameter and 391. 7 mm in lengthfollowed by drying to form an electrophotographic photoconductorconsisting of an undercoat layer of 3.5 μm, a charge generating layer of0.2 μm, a charge transporting layer of 22 μm, and a protective layer of2 μm. <Undercoat layer coating solution> Titanium dioxide powder 400parts Melamine resin 65 parts Alkyd resin 120 parts 2-Butanone 400 parts<Charge generating layer coating solution> Azobis pigment of thefollowing structure 8 parts

Trisazo pigment having the following structure 6 parts

Polyvinyl butyral 5 parts 2-Butanone 200 parts Cyclohexane 400 parts<Charge transporting layer coating solution> A-type polycarbonate 10parts Charge transporting material of the following 7 parts structuralformula

Tetrahydrofurane 400 parts Cyclohexanone 150 parts <Protective layercoating solution> A-type polycarbonate 10 parts Charge transportingmaterial of the following 8 parts structural formula

Tetrafluoroethylene particle 4 parts (Specific resistance: 1 × 10¹⁵Ω ·cm, average primary particle diameter: 0.3 μm) Tetrahydrofurane 400parts Cyclohexanone 150 parts

[0269] (Preparation of Photoconductor (b))

[0270] A photoconductor (b) was obtained in the same manner as in thephotoconductor (a) except using alumina fine particle instead of thetetrafluoroethylene particle of the protective layer coating solutionmaterial in the photoconductor (a).

[0271] (Preparation of Photoconductor (c))

[0272] A photoconductor (c) was obtained in the same manner as in thephotoconductor (a) except changing the protective layer coating solutionto the following one. <Protective layer coating solution> High molecularcharge transporting material of the 18 parts following structuralformula

Tetrafluoroethylene particle 4 parts (Specific resistance: 1 × 10¹⁵Ω ·cm, average primary particle diameter: 0.3 μm) Tetrahydrofurane 400parts Cyclohexanone 150 parts

[0273] (Preparation of Photoconductor (d))

[0274] A photoconductor (d) was obtained in the same manner as in thephotoconductor (a) except not using the tetrafluoroethylene particle ofthe protective layer coating solution material in the photoconductor(a).

[0275] (Preparation of Photoconductor (e))

[0276] A photoconductor (e) was obtained in the same manner as in thephotoconductor (a) except using no charge transporting material in theprotective layer coating solution of the photoconductor (a).

[0277] (Preparation of Photoconductor (f))

[0278] A photoconductor (f) was obtained in the same manner as inphotoconductor (a) except changing the protective layer coating solutionto a one having the following composition. <Protective layer coatingsolution> A-type polycarbonate 10 parts Charge transporting material ofthe following 8 parts structural formula

Alumina fine particle 4 parts (Specific resistance: 2.5 × 10¹²Ω · cm,average primary particle diameter: 0.4 μm) Unsaturated polycarboxylicpolymer solution 0.1 parts (Acid value: 180 mgKOH/g, made by BYK CHEMIE)Tetrahydrofurane 400 parts Cyclohexanone 150 parts

[0279] (Preparation of Photoconductor (g))

[0280] A photoconductor (g) was obtained in the same manner as in thephotoconductor (b) except changing the protective layer coating solutionto a one having the following composition. <Protective layer coatingsolution> A-type polycarbonate 10 parts Charge transporting material ofthe following 8 parts structural formula

Alumina fine particle 4 parts (Specific resistance: 2.5 × 10¹²Ω · cm,average primary particle diameter: 0.4 μm) Methylphenyl silicone oil(SINETSU SILICONE: KF 50) 0.1 part Tetrahydrofurane 400 partsCyclohexanone 150 parts

[0281] (Preparation of Photoconductor (h))

[0282] A photoconductor (h) was prepared in the same manner as in thephotoconductor (a) except changing the charge generating layer coatingsolution to a one having the following composition. <Charge generatinglayer coating solution> Titanyl phthalocyanine having a spectrum  3parts shown in FIG. 8 Polyvinyl butyral  2 parts 2-Butanone 120 parts

[0283] (Preparation of Photoconductor (i))

[0284] In the preparation example of the photoconductor (h), theconductive support was anodized as follows, and the charge generatinglayer, the charge transporting layer and the protective layer wereprovided in the same manner as the preparation example of thephotoconductor (h) without providing any undercoat layer to obtain aphotoconductor (i).

[0285] <Anodic Treatment>

[0286] The support surface was finished by mirror polishing followed bydegreasing and washing with water, and then dipped in an electrolyticcell of temperature 20° C. and sulfuric acid 15 vol % to anodize it atan electrolytic voltage 15V for 30 min. After washing with water, asealing treatment was performed using 7% nickel acetate aqueous solution(50° C.). Thereafter, a washing with pure water was performed to obtaina support having an anodic oxide film of 6 μm formed thereon.

Example 1

[0287] An actual use evaluation was carried out using the product tonerA and the photoconductor (a).

Example 2

[0288] An actual use evaluation was carried out using the product tonerB and the photoconductor (b).

Example 3

[0289] An actual use evaluation was carried out using the product tonerC and the photoconductor (c).

Example 4

[0290] An actual use evaluation was carried out using the product tonerD and the photoconductor (a).

Example 5

[0291] An actual use evaluation was carried out using the product tonerB and the photoconductor (c).

Example 6

[0292] An actual use evaluation was carried out using the product tonerA and the photoconductor (e).

Example 7

[0293] An actual use evaluation was carried out using the product tonerA and the photoconductor (f).

Example 8

[0294] An actual use evaluation was carried out using the product tonerA and the photoconductor (g).

Example 9

[0295] An actual use evaluation was carried out using the product tonerA and the photoconductor (h).

Example 10

[0296] An actual use evaluation was carried out using the product tonerA and the photoconductor (i).

Comparative Example 1

[0297] An actual use evaluation was carried out using the product tonerE and the photoconductor (d).

Comparative Example 2

[0298] An actual use evaluation was carried out using the product tonerE and the photoconductor (c).

Comparative Example 3

[0299] An actual use evaluation was carried out using the product tonerF and the photoconductor (c).

[0300] [Actual Use Evaluation]

[0301] For the toners and photoconductors obtained in Examples andComparative Examples, a copy test was carried out using a modifiedmachine of “IPSIO Color 5000” made by RICHO to evaluate the followingitems. The modified machine was set to a state allowing the collectionof eight A4 full-color copies per min by raising the processing speed of“Color 5000”. The copy test was carried out in a 30,000-sheet full-colormode including black (working environment: 23° C., 55%RH). Just afterstarting the copy test and after 30,000-sheet copying, the filming tophotoconductor and cleaning member, the scraping (wear) ofphotoconductor, and the image density of the resulting image weremeasured to evaluate the image quality.

[0302] The image density was measured using “X-rite 938” (made byX-RITE). The image quality was evaluated by visually observing whetherdensity unevenness, resolution deterioration, or the like is present inthe image or not.

[0303] [Physical Property Measurement]

[0304] The angle of repose 3 was measured according to theabove-mentioned method. The flowchart of the measuring work is shown inFIG. 7.

[0305] The physical properties of the toners used in Examples andComparative Examples are shown in Table 1, and the angle of repose androundness of each toner used and the image evaluation result are shownin Table 2. TABLE 1 List of Toner Physical Properties Specific WeightSurface Area Content of Specific Specific Specific Volume of PulverizedPulverized Surface Surface Surface Average Colored Colored Area ofContent of Area of Content of Area of Content of Particle ParticleParticle Additive 1 Additive 1 Additive 2 Additive 2 Additive 3 Additive3 diameter H W Ht1 Wt1 Ht2 Wt2 Ht3 Wt3 (μm) (m²/g) (wt %) (m²/g) (wt %)(m²/g) (wt %) (m²/g) (wt %) Z Product 6.38 2.48 98.3 140 0.7 50 0.5 650.5 0.64 Toner A Product 6.38 2.48 98.5 230 0.5 50 0.5 65 0.5 0.71 TonerB Product 6.38 2.48 97.5 200 0.8 50 1.2 65 0.5 1.04 Toner C Product 6.692.34 98.3 140 0.7 50 0.5 65 0.5 0.68 Toner D Product 5.36 4.12 98.5 1401.0 — — 65 0.5 0.43 Toner E Product 6.69 2.34 96.7 230 1   50 1.8 65 0.51.56 Toner F

[0306] TABLE 2 Angle Filming Scraped amount of Filming to to of Un evenPhoto Repose Cleaning Photo- Photoconductor Image Image Toner conductorZ (°) Roundness Member conductor (μm) Density Density Resolution Ex. 1 Aa 0.64 23 0.96 ◯ ◯ 1.5 1.5 ◯ ◯ Ex. 2 B b 0.71 19 0.95 ◯ ◯ 1.7 1.6 ◯ ◯Ex. 3 C c 1.04 15 0.96 ◯ ◯ 1.9 1.7 ◯ ◯ Ex. 4 D a 0.68 22 0.95 ◯ ◯ 1.61.5 ◯ ◯ Ex. 5 B c 0.71 20 0.95 ◯ ◯ 1.7 1.6 ◯ ◯ Ex. 6 A e 0.64 24 0.96 ◯◯ 1.3 1.3 ◯ ◯ Ex. 7 A f 0.64 22 0.96 ◯ ◯ 1.4 1.5 ◯ ⊚ Ex. 8 A g 0.64 160.96 ◯ ⊚ 1.0 1.5 ◯ ◯ Ex. 9 A h 0.64 23 0.96 ◯ ◯ 1.5 1.7 ◯ ⊚ Ex. 10 A i0.64 23 0.96 ◯ ◯ 1.5 1.7 ⊚ ◯ Comp. E d 0.43 36 0.93 X X 2.6 1.2 X X Ex.1 Comp. E c 0.43 33 0.93 X X 2.3 1.2 X X Ex. 2 Comp. F c 1.56 10 0.95 XX 5.2 1.0 X Δ Ex. 3

[0307] As is apparent from Table 2, the toners and photoconductors ofExamples 1-10 of the present invention show satisfactory performancesfor the filming to photoconductor and cleaning member, the scraping ofphotoconductor, and the image density, uneven image desity andresolution of the resulting image in the 30,000-sheet copy test usingthe modified machine of “IPSIO Color 5000” made by RICHO, and have noproblem from the point of maintenance property.

[0308] In Example 6 where no charge transporting material is added tothe protective layer, the image density is slightly deteriorated,compared with Example 1, and it shows that the addition of the chargetransporting material is effective. In the comparison of Example 7 withExample 1, the filler dispersing state of the protective layer wassatisfactory in Example 7, and the resolution was consequentlysatisfactory. This shows that it is effective to include an organiccompound with acid value of 10-400 (mgKOH/g) in the protectively layer.In the comparison of Example 8 with Example 1, the addition of a largequantity (a quantity as silicone oil is present as droplets) of siliconeoil to the protective layer reduces the surface energy of thephotoconductor, resulting in a reduction in the angle of repose, whichapparently allows the prevention of the filming to photoconductor. Thewear of the photoconductor was also minimized, which shows that such anaddition is apparently contributable to the improvement of durability.In the comparison of Example 9 with Example 1, the recording lightquantity could be rather reduced because the photoconductor of Example 9was more sensitive. Consequently, the resolution could be improved. Inthe comparison of Example 10 with Example 1, the photoconductor ofExample 10 was more stable in electrostatic property, and an image freefrom uneven image desity could be outputted.

[0309] For the toners and photoconductors of Comparative Examples 1-3,no particular problem arose in the initial stage, but the filming tophotoconductor and cleaning member occurred after 30,000-sheet run, thescraped amount of photoconductor was increased, and the densityreduction, uneven image desity and reduction in resolution of theresulting image also occurred.

Example 11

[0310] The charger of the copying machine used in Example 1 or ascorotron charger was changed and remodeled to a contact type chargeroller, and a 30,000-sheet continuous copy was carried out in the samemanner as in Example 1. The unexposed part potential of thephotoconductor was adjusted so as to be the same as in Example 1(−650V).

Example 12

[0311] The charger of the copying machine used in Example 11 or thecontract type charge roller was changed and remodeled to the followingcharge roller, and a 30,000-sheet continuous copy was carried out in thesame manner as in Example 11. The applied voltage was set to only the DCcomponent similarly to Example 11.

[0312] <Charge roller>

[0313] A Teflon tape 80 μm thick was wound on both ends 5 mm (theseareas are non-image forming portions) of the charge roller of Example 11to form an adjacent arrangement charge roller as shown in FIG. 5.

Example 13

[0314] The continuous copy was carried out except changing the chargecondition of Example 12 as follows.

[0315] <Charging Condition>

[0316] Unexposed part potential −650 V

[0317] As an AC component, −1.2 kV was applied by peak-to-peak.

[0318] After the 30,000-continuous runs of Examples 1 and 11-13, ahalftone image was outputted under high temperature and high humidity(30° C., 90%RH) and evaluated for image quality. The result is shown inTable 3. TABLE 3 Halftone Image Note Example 1 Slight reduction inStrong ozone odor resolution during continuous copying Example 11 Slighttoner deposition caused by blotted charge roller Example 12 unevendensity slightly observed based on uneven charge Example 13 Good

[0319] The problems in Examples 1, 11 and 12 are not in a practicallyserious level, but the condition of Example 13 is most excellent.

Example 14

[0320] Under the same condition as in Example 1, a 50,000-sheetcontinuous copy was carried out.

Example 15

[0321] The copying machine of Example 14 was remodeled, and a zincstearate supplying member (a mechanism for pressing bar-like zincstearate for 10 sec after 100-sheet run) was provided between thecleaning member and the charging member. Under this condition, adurability test was performed in the same manner as in Example 14.

Example 16

[0322] A durability test was performed in the same manner as Example 14except adding 0.15 wt % of powdered zinc stearate to the toner suppliedto the developing portion in Example 14.

Example 17

[0323] A durability test was performed in the same manner as Example 16except repeating, as the non-image forming operation, only the exposureup to the bright part potential, the toner development thereto by thedeveloping portion, and the recovering operation of the toner on thesurface of photoconductor by the cleaning portion for 20 sec every1000-sheet passing.

[0324] After the execution of Examples 14-17, an image output wasperformed under a high-temperature and high-humidity environment. Thesurface of photoconductor was observed after the end of the experiment.The result is shown in Table 4. TABLE 4 Image (after 50,000-sheet run)Others Example 14 Extremely slight Extremely slight filming imageomission Example 15 Good Satisfactory image without any filming. Example16 Good Satisfactory image without any filming. Slight image blurring inimage output under high temperature and high humidity after run. Example17 Good Satisfactory image without any filming. No image blurring evenunder high temperature and high humidity.

[0325] Under the condition of Example 14, the surface of photoconductorwas slightly filmed when the durability test was performed up to 50,000sheets, and an image omission according thereto occurred (but it is notin a serious level). In contrast, the filming could be prevented bysupplying zinc stearate to the surface of photoconductor as in Examples15 and 16. Further, the cleaning operation for surface of photoconductorwas performed as in Example 17, whereby the image blurring could beperfectly eliminated even under the high temperature and high humidity(30° C., 90% RH).

[0326] (Preparation of Photoconductor (j))

[0327] A photoconductor (j) was prepared in the same manner as in thephotoconductor (f) except changing the protective layer coating solutionin the photoconductor (f) to a one having the following composition.<Protective Layer Coating Solution> A-type polycarbonate 10 parts Chargetransporting material of the following 8 parts structural formula

Titanium oxide fine particle 4 parts (Specific resistance: 1.5 × 10¹⁰Ω ·cm, average primary particle diameter: 0.5 μm) Unsaturatedpolycarboxylic polymer solution 0.1 parts (Acid value: 180 mgKOH/g, BYKCHEMIE) Tetrahydrofurane 400 parts Cyclohexanone 150 parts

[0328] (Preparation of Photoconductor (k))

[0329] A photoconductor (k) was prepared in the same manner as in thephotoconductor (f) except changing the protective layer coating solutionin the photoconductor (f) to a one having the following composition.<Protective Layer Coating Solution> A-Type polycarbonate 10 parts Chargetransporting material of the following 8 parts structural formula

Tin oxide-antimony oxide powder 4 parts (Specific resistance: 1 × 10⁶Ω ·cm, average primary particle diameter: 0.4 μm) Unsaturatedpolycarboxylic polymer solution 0.1 parts (Acid value: 180 mgKOH/g, madeby BYK CHEMIE) Tetrahydrofurane 400 parts Cyclohexanone 150 parts

Examples 18 and 19]

[0330] The thus-prepared photoconductors (j) and (k) were subjected foractual use evaluation using the product toner A in the same manner as inExample 7.

[0331] The result is shown in Table 5 together with that of Example 7.TABLE 5 Angle Scraped of Filming to Filming to amount of Uneven Photo-Repose Cleaning Photo- Photoconductor Image image Toner conductor Z (°)Roundness Member conductor (μm) Density desity Resolution Example A f0.64 22 0.96 ◯ ◯ 1.4 1.5 ◯ ⊚ 7 Example A j 0.64 22 0.96 ◯ ◯ 1.3 1.4 ◯ ◯18 Example A k 1.64 22 0.96 ◯ ◯ 1.4 1.3 Δ Δ 19

[0332] According to the present invention, in a method for forming anelectrophotographic image for forming an image on a transfer material atleast by the steps for charging, exposing, developing and transferring,and recovering the toner remained untransferred in the step forcleaning, the toner of the step for developing has a total surface arearatio Z of additive, which is calculated by the above-mentionedequation: Z=(Ht·Wt)/(H·W), satisfying 0.5≦Z≦1.5, the photoconductor usedcomprises at least a photosensitive layer and a filler-containingprotective layer on a conductive support, and the angle of repose of thetoner to the protective layer surface of the photoconductor is 30° orless. Such an image forming method and electrophotographic device isused, whereby an image of high quality for image density, uneven imagedesity, and resolution can be obtained, the filming to photoconductorand cleaning member never occurs, and the scraping of photoconductor canbe prevented.

What is claimed is:
 1. A method for forming an electrophotographic imagecomprising; a step for charging an electrophotographic photoconductor; astep for exposing the electrophotographic photoconductor charged in thestep for charging imagewisly to form an electrostatic latent image; astep for developing by supplying a toner to the electrostatic latentimage to visualize the electrostatic latent image, and forming adeveloped image; a step for transferring the developed image formed inthe step for developing onto a recording material; and a step forcleaning by recovering the toner remained untransferred on theelectrophotographic photoconductor, wherein the toner comprises a tonerparticle and an additive having a total surface area ratio Z of theadditive in the toner, expressed by Z=(Ht·Wt)/(H·W), satisfies0.5≦Z≦1.5; and the electrophotographic photoconductor comprises at leasta photosensitive layer and a filler-containing protective layer providedon a conductive support in that order, and an angle of repose of thetoner to the protective layer surface of the electrophotographicphotoconductor being 30° or less (where numerals in the formula express:H: Specific surface area of toner particles (m²/g) W: Weight content oftoner particles (%) Ht: Specific surface area of additives (m²/g) Wt:Content of additives (%)).
 2. A method for forming anelectrophotographic image according to claim 1, wherein the toner is aspherical toner having a roundness of 0.95 or more.
 3. A method forforming an electrophotographic image according to claim 1, wherein thefiller contained in the filler-containing protective layer is aninorganic pigment or metal oxide having a specific resistance of 1×10¹⁰Ω·cm or more.
 4. A method for forming an electrophotographic imageaccording to claim 1, wherein the filler-containing protective layercontains a charge transporting material.
 5. A method for forming anelectrophotographic image according to claim 4, wherein the chargetransporting material is a polymer having electron-donating group.
 6. Amethod for forming an electrophotographic image according to claim 1,wherein the filler-containing protective layer contains an organiccompound having acid value of 10-400 (mgKOH/g).
 7. A method for formingan electrophotographic image according to claim 1, wherein silicone oilcompatible with a material constituting the protective layer of theelectrophotographic photoconductor is added to the protective layer inan amount exceeding the limit of the compatibility with the materialconstituting the protective layer.
 8. A method for forming anelectrophotographic image according to claim 1, wherein theelectrophotographic photoconductor contains a charge generating materialthat is titanyl phthalocyanine having a maximum diffraction peak atleast at 27.2° as the diffraction peak (±0.2°) of Bragg angle 2θ tocharacteristic X-rays (wavelength 1.542 Å) of CuKα.
 9. A method forforming an electrophotographic image according to claim 1, wherein theelectrophotographic photoconductor contains a charge generating materialthat is an azo pigment expressed by the following general formula (A).

[where Cp₁ and Cp₂, which may be the same or may be different, eachrepresents a coupler residue; R₂₀₁ and R₂₀₂, which may be the same ormay be different, each represents a hydrogen atom, a halogen atom, analkyl group, an alkoxyl group, or a cyano group; and Cp₁ and Cp₂ aregroups expressed by the following general formula (B).

[where R₂₀₃ represents a hydrogen atom, an alkyl group, or an arylgroup; R₂₀₄, R₂₀₅, R₂₀₆, R₂₀₇, and R₂₀₈ each represents a hydrogen atom,a nitro group, a cyano group, a halogen atom, a trifluoromethyl group,an alkyl group, an alkoxyl group, a dialkylamino group, or a hydroxylgroup; and Z represents an atom group necessary for constituting asubstituted or non-substituted aromatic carbocyclic residue or asubstituted or non-substituted aromatic heterocyclic residue].
 10. Amethod for forming an electrophotographic image according to claim 1,wherein the conductive support surface of the electrophotographicphotoconductor is anodized.
 11. A method for forming anelectrophotographic image according to claim 1, further comprising astep for supplying and applying zinc stearate onto the surface of theelectrophotographic photoconductor.
 12. A method for forming anelectrophotographic image according to claim 1, wherein the tonercontains powdered zinc stearate.
 13. An electrophotographic devicecomprising; an electrophotographic photoconductor; means for chargingthe electrophotographic photoconductor; means for exposing theelectrophotographic photoconductor charged by the means for chargingimagewisly to form an electrostatic latent image; means for developingby supplying a toner to the electrostatic latent image to visualize theelectrostatic latent image, and forming a developed image; means fortransferring the developed image developed by the means for developingonto a recording material; and means for cleaning by recovering thetoner remained untransferred on the electrophotographic photoconductor,wherein the toner comprises a toner particle and an additive having atotal surface area ratio Z of the additive in the toner, expressed byZ=(Ht·Wt)/(H·W), satisfies 0.5≦Z≦1.5; and the electrophotographicphotoconductor comprises at least a photosensitive layer and afiller-containing protective layer provided on a conductive support inthat order, and an angle of repose of the toner to the protective layersurface of the electrophotographic photoconductor being 30° or less(where numerals in the formula express: H: Specific surface area oftoner particles (m²/g) W: Weight content of toner particles (%) Ht:Specific surface area of additives (m²/g) Wt: Content of additives (%)).14. An electrophotographic device according to claim 13, wherein thetoner is a spherical toner having a roundness of 0.95 or more.
 15. Anelectrophotographic device according to claim 13, wherein the fillercontained in the filler-containing protective layer is an inorganicpigment or metal oxide having a specific resistance of 1×10¹⁰ Ω·cm ormore.
 16. An electrophotographic device according to claim 13, whereinthe filler-containing protective layer contains a charge transportingmaterial.
 17. An electrophotographic device according to claim 16,wherein the charge transporting material is a polymer havingelectron-donating group.
 18. An electrophotographic device according toclaim 13, wherein the filler-containing protective layer contains anorganic compound having acid value of 10-400 (mgKOH/g).
 19. Anelectrophotographic device according to claim 13, wherein silicone oilcompatible with the material constituting the protective layer of theelectrophotographic photoconductor is added to the protective layer inan quantity exceeding the limit of the compatibility with the materialconstituting the protective layer.
 20. An electrophotographic deviceaccording to claim 13, wherein the electrophotographic photoconductorcontains a charge generating material that is titanyl phthalocyaninehaving a maximum diffraction peak at least at 27.2° as the diffractionpeak (±0.2°) of Bragg angle 2θ to characteristic X-rays (wavelength1.542 Å) of CuKα.
 21. An electrophotographic device according to claim13, wherein the electrophotographic photoconductor contains a chargegenerating material that is an azo pigment expressed by the followinggeneral formula (A):

[where Cp₁ and Cp₂, which may be the same or may different, eachrepresents a coupler residue; R₂₀₁ and R₂₀₂, which may be the same ormay be different, each represents hydrogen atom, a halogen atom, analkyl group, an alkoxyl group, and a cyano group; and Cp₁ and Cp₂ aregroups expressed by the following general formula (B):

(where R₂₀₃ represents hydrogen atom, an alkyl group, or an aryl group;R₂₀₄, R₂₀₅, R₂₀₆, R₂₀₇, and R₂₀₈ each represents hydrogen atom, nitrogroup, cyano group, a halogen atom, trifluoromethyl group, an alkylgroup, an alkoxyl group, a dialkylamino group, or hydroxyl group; and Zrepresents an atom group necessary for constituting a substituted ornon-substituted aromatic carbocyclic residue or a substituted ornon-substituted aromatic heterocyclic residue).
 22. Anelectrophotographic device according to claim 13, wherein the conductivesupport surface of the electrophotographic photoconductor is anodized.23. An electrophotographic device according to claim 13, wherein themeans for charging comprises a charging member arranged in contact withthe electrophotographic photoconductor or arranged adjacently thereto.24. An electrophotographic device according to claim 23, wherein thecharging member arranged adjacently to the electrophotographicphotoconductor has a gap therebetween of 200 μm or less.
 25. Anelectrophotographic device according to claim 23, wherein the chargingmember forms an electric field comprising an AC component superimposedon a DC component, and charges the electrophotographic photoconductor bythe electric field.
 26. An electrophotographic device according to claim13, wherein the electrophotographic device further comprises a memberfor supplying and applying zinc stearate onto the surface of theelectrophotographic photoconductor.
 27. An electrophotographic deviceaccording to claim 13, wherein the toner contains powdered zincstearate.